Abstract:    Under the technology decoupling of China from the US, overcoming the "neck strangling" challenges posed by key core technologies has become a primary problem for Chinese mega-projects. Based on the innovation ecosystem theory, using a longitudinal single case analysis, this paper explored the mechanism of collaborative innovation among numerous participants in mega-projects to analyze the "catch-up" process of China′s high-speed railway technology. The results indicated that: (1) the changes in core platform promote the evolution of the innovation ecosystem; (2) the collaboration models and mechanisms of collaborative innovation among participants evolve at different stages of the innovation ecosystem′s development in mega-projects; and (3) collaboration among institutions, organizations, and knowledge interacts mutually, supporting and promoting the formation, evolution, and technological innovation efficiency of the innovation ecosystem. The study will enrich the theoretical framework of innovation ecosystems based on Chinese practices, expand the scope of research on platform theory and collaborative innovation theory, and provide enlightenment for overcoming the "neck strangling" dilemma of critical core technologies in mega-projects in China.

Key words: innovation ecosystem, collaborative innovation, mega-project, technological innovation, China′s high-speed railway