Starting from knowledge breadth and knowledge depth， it explored the influence mechanism of firms’ knowledge base on value co-creation in the innovation ecosystem， and constructed a moderated mediation model by introducing the degree of participation and supports of auxiliary institutions. Based on the research data of high-tech firms， it tested the hypothesis with hierarchical regression analysis and bootstrap method. The results show that knowledge breadth positively influences value co-creation， while there is an inverse U relationship between knowledge depth and value co-creation； the degree of participation has a partial mediating effect between knowledge base and value co-creation， and supports of auxiliary institutions significantly moderate the relationship between knowledge base and degree of participation. It analyzed the value co-creation mechanism of innovation ecosystem from the perspectives of internal knowledge base and external relationship characteristics， not only enriching the research content of knowledge management in innovation ecosystem， but also providing decision reference and practical insight for enterprises to cultivate innovation ecosystem and realize value co-creation.