Abstract: Social e-commerce is a new business model that integrates social network and e-commerce. In the era of mobile internet, it opens up a new space for the development of network economy. Trust is an important mechanism for the development of social e-commerce platform. The paper studies the transformation mechanism and factors which affect the user ‘s trust on social e-commerce platform, analyzes multi-stage and multi-dimensional factors of trust based on the grounded theory, and constructs a dynamic hierarchical upgrading theoretical model of trust mechanism from the embedded perspective. The findings show that the embedding stage between the user and platform is divided into relational embeddedness, structural embeddedness and cognitive embeddedness, which corresponds to the evolving path of “identity trust-behavioral trust-cognitive trust-emotional trust”. The factors which affect the transformation path are relationship network, structure system and quality effect. The conclusion enriches the theoretical connotation of trust mechanism of e-commerce platform, and there will be certain theoretical guidance and practical enlightenment for the development of domestic social e-commerce platform.