With the massive access of power electronic devices in the microgrid, the dynamic characteristics of multiple power sources and loads are coupled with each other, which makes the problem of stability analysis in the microgrid system become a hot spot. In this paper, based on the virtual synchronous motor control of microgrid systems, a multi-distributed power system nonlinear state-space modeling method is proposed, and a unified state-space equation of microgrid with distributed power, line and load is established. Based on the established state-space equation, the eigenvalue analysis is used to study the factors that affect the stability of the microgrid system. Then the bifurcation theory is used to study the influence of the key parameters of the virtual synchronous motor control and the system topology parameters on system stability. The microgrid model based on virtual synchronous motor control is built on the PSCAD/ETMDC simulation platform, which verifies the correctness and effectiveness of the proposed method. This work is supported by National Key Research and Development Program of China (No. 2017YFB0903601), National Natural Science Foundation of China (No. 51777088), and Science and Technology Project of the Headquarter of State Grid Corporation of China in 2018 “Research and Application of Pre-installed Microgrid Energy-storage Substation Optimization Integration Techniques” (No. SGNXDK00DWJS1800016).