Abstract: This paper studies the structure and collaborative mechanism of innovation ecosystem at firm level based on a grounded analysis about Haier Group. The findings show a special cross-layer nested structure of Haier’s innovation ecosystem during its construction process and besides, we find four critical unique collaborative mechanisms in this special structure: coupled platform modular, multilateral network cooperation, internal competition design and hierarchical ecological management, which are not common used in normal innovation ecosystem at macro level. This paper has two important contributions to extant literature about innovation ecosystem: (1) we propose firm-level innovation ecosystem, where actors from inner-enterprises can take part in inside and outside ecological activities as independent subjects simultaneously, and form cross-layer nested structures. This finding breaks the limitation of extant literatures which only focus on innovation system at macro level and treat firms as closed homogeneous nodes. (2) this paper proposes that the collaboration of innovation ecosystem can be fulfilled by the logic of network effect and authority, where previous studies majorly focus on persistent leader intervention and resource investment.