Abstract: This paper takes the Chinese start-up companies as empirical research objects to explore the impact of openness on start-up companies’ innovation performance considering the role of absorptive capacity and market environment in order to further study the mechanism of the impact. The article adopts multiple regression and other methods to empirically analyze the 223 sets of valid data. The results show that openness and absorptive capacity have a positive impact on the innovation performance of start-up companies; openness has a positive impact on absorptive capacity; absorptive capacity plays a partial intermediary role between openness and innovation performance; The market environment moderates the relationship between openness and innovation performance.