Today, a society can move forward and rapidly in the path of development, equipping itself with productive entrepreneurial knowledge and skills by creating the necessary resources to use this valuable capability, other resources of the society to create value and achieve growth and development, Manage and direct. Promoting entrepreneurship requires an ecosystem. The aim of this study is to identify the role of accelerators in the development of entrepreneurial ecosystem using an open innovation approach. The design of this research is qualitative (multiple case study) and is fundamental in terms of research method. Therefore, semi-structured interviews were conducted with 20 main human resources of Kermanshah accelerator centers, which were selected using judgmental sampling method. In the present study, a two-stage coding method was used to analyze the interview findings. Finally, according to the research findings and coding, the role of business accelerator centers on the development of entrepreneurial ecosystem using an open innovation approach in two parts before the start-up and after the start-up has been identified and studied. The results show that accelerators, by creating a coordinated network between the actors of the startup ecosystem and the entrepreneurial ecosystem and their partners, Creating relationships based on common vertical and horizontal connections between ecosystem actors, Creating value in predetermined partnerships and programs and creating a network of communication between ecosystem actors and networks and companies outside the ecosystem play a role in the development of the entrepreneurial ecosystem.