Abstract: Greenhouse gas (GHG) emissions inventory is the fundamental data for low carbon city development. There are significant methodology differences between the national inventory and city inventory. The system and accounting model as well as principles, boundaries and scope of well accepted urban GHG inventory are introduced. Based on the characteristics of city, the mixed accounting model, boundaries, and the emission scope of city GHG inventory are analyzed. The difficulties and challenges in the study of the GHG inventory of cites in China are raised and suggestions proposed as well.