Abstract: DC microgrid will be the main power supply system for the future sustainable homes and buildings due to their high controllability, reliability, and system-level stability which are important to the design of the DC power supply system. In this paper, the common mathematic model of DC microgrid under the distributed control strategy was built, and based on this model, large signal stability was studied which Lyapunov’s direct method, the parameter boundary conditions of DC microgrid were estimated. Based on the analysis of the influence of small disturbance on bus voltage, a stability test method of parallel impedance in DC microgrid was proposed. It provided an important reference for the DC microgrid system-level design. The simulation results show that the stability of the DC microgrid can be tested by the proposed method.