Green Smart City (GSC), is one of the new types of cities which integrates eco-concepts and information technologies. As GSC construction is a resource intensive process, it requires a large amount of knowledge, information, talent and capital. Thus, setting up an innovation ecosystem is an astute way to promote the construction of a GSC. This paper, based on the case study by the Insigma Group, tries to explore the rules of innovation ecosystem building for the construction of GSCs in China.