Abstract: Under the background of digital economy, how to efficiently orchestrate other actors’ resources in the platform to achieve value creation is the core issue for digital platform firms to cope with highly uncertain environmental challenges. However, there is a lack of in-depth research on the unique process mechanism of resource orchestration for digital platform firms. Opportunity set provides a new perspective for this paper to reveal the resource orchestration process mechanism of digital platform firms. Based on the LCOR entrepreneurship theory, digital platform firms will continue to build opportunity set in the process of orchestrating other actors’ resources in the platform, which can further guide the orchestration of resources. Moreover, the continuous interaction between opportunities and resources is conducive to the creation of value. Nevertheless, few scholars have deeply explored the relationship between resource orchestration and opportunity set of digital platform firms. Therefore, this paper uses the Rootcloud case to analyze the resource orchestration process mechanism of digital platform firms from the opportunity set perspective, based on the construction logic of "dimensions development of the core concept—description of the relationship between concepts—analysis of the relationship effect results". It is found that the resource orchestration of digital platform firms includes three dimensions: resource sharing, resource coordination and resource renewal. The interaction between resource orchestration and opportunity set based on effectuation and causation iterative logic is the deep mechanism of resource orchestration process of digital platform firms. The interaction between resource orchestration and opportunity set is beneficial to digital platform firms’ value creation. The theoretical contributions of this research are as follows: Firstly, under the digitalization context, this paper gives new meanings to resource sharing and resource coordination, then refines the new dimension of resource renewal to show the uniqueness of resource orchestration in digital platforms. Furthermore, we reveal the influence mechanism of digital platform firms’ resource orchestration process on value creation from the opportunity set perspective, enriching and expanding resource orchestration theory. Secondly, this study deeply reveals the relationship between digital platform firms’ resource orchestration and opportunity set based on the logic of effectuation and causation iteration, which lays the foundation for the construction of opportunity set theory under the digitalization context. Thirdly, by analyzing the interactive mechanism between resource orchestration and opportunity set of digital platform firms, this research emphasizes the key role of data resources and multi-actor, and reveals the dynamic matching mechanism between opportunities and resources at inter-organizational level under the digitalization context, expanding LCOR entrepreneurship theory. The conclusions of this paper provide important insights for the resource orchestration practice of digital platform firms in China. Specifically, it can help digital platform firms make full use of digital technologies and data resources for resource sharing, resource coordination and resource renewal with other actors in the platform. Moreover, our findings lead digital platform firms to think about the logic of converting platform resources into value from the perspective of opportunity set, which is conducive for them to promote the interaction between resource orchestration and opportunity set, so as to realize the creation of economic and social value.