Abstract: Both the international leading customers and domestic university-industry collaboration have important impact on the catch-up of latecomer firms. On one hand, cooperation with international leading customers will help latecomer firms to enhance market capability. The international leading customers can help latecomers to enter the global value chain in the form of OEM production to learn skill and process technology, but many latecomers would fall into the trap of long-term low value-added OEM after obtaining initial success in product processing, and it is difficult to carry out higher technological upgrading. On the other hand, university-industry collaboration will help latecomer firms improve their technological capability. The university-industry collaboration has always been an important national policy of the Chinese government to promote technological innovation, and many Chinese manufacturing firms have carried out various types of university-industry collaboration to improve their technological innovation capability. Through university-industry collaboration, latecomer firms can improve their absorptive capacity, so as better to identify, digest and absorb technological knowledge. However, in the process of practice, many university-industry collaboration have caused the problem of "marginalization of R&D" due to the separation of research activities from production and insufficient engineering capability, and there is a practical problem of relatively low efficiency in Chinese domestic university-industry collaboration. Therefore, connecting the international leading customers and improving the university-industry collaboration system simultaneously have become the core elements of catch-up successfully for latecomer firms. However, it is worth concern that there is currently a lack of relevant research linking the dynamics of both domains. Longitudinal case study can show the dynamic process of phenomena changing over time, and reveal how the dynamic mechanism behind the phenomenon works. Through the method, this paper explores the detail process of how the international leading customers and university-industry collaboration coevolve in the process of catch-up of latecomer firms. Based on the principle of theoretical sampling, Ningbo Novel Optics Co., Ltd. was selected as the case study sample. First, Novel Optics has achieved a catch-up transformation from process technology to design technology. Second, both international leading customers and domestic university-industry collaboration play important role in the catch-up process. Novel Optics has carried out close cooperation with international leading customers and many domestic universities and institutes, which has greatly enhanced its technological innovation and market capabilities. Through the longitudinal case analysis of Novel Optics from 1997 to 2021, this paper finds that the latecomer firms will realize the catch-up transformation from the process technology stage to the design technology stage, the connection between international leading customers and domestic university-industry collaboration should transform from echoing mechanism to synchronizing mechanism. In the process technology stage, the international leading customers direct the processing needs of mature products, so the knowledge characteristics of the technology are relatively low, the market demand is more certain, and the latecomer firms can connect the international leading customers with domestic university-industry collaboration through the echoing mechanism. The improvement of technology brings the improvement of product performance, latecomer firms can use the scale effect to further reduce product costs, and bring more value to the leading international customers. Subsequently, the market capability of latecomers will also increase. In the design technology stage, because the product is still in the development stage or even the research stage, both architecture design and component design have not yet been finalized, the knowledge characteristics of the technology and the uncertainty of market demand are high relatively, therefore, the latecomers need the synchronizing mechanism to connect the international leading customers with the domestic university-industry collaboration. This paper introduces the perspective of coevolution, which enriches the catch-up theory of latecomer firms. Based on the context of Chinese latecomer firms, it proposes a sustained catch-up path for the coevolution between the international leading customers and domestic university-industry collaboration. The paper not only makes up for the traditional deficiency from the single perspective of the leading international firms or university-industry collaboration to examine the catch-up of latecomer firms, but also provides a new mechanism for technological catch-up in the context of Chinese latecomer firms. These conclusions have also important enlightenment for the catch-up practice of latecomer firms and the self-reliance and self-improvement of Chinese science and technology.