Abstract: The DC micro-grids architecture based on multistage power converter was studied, the research method of constant power load was proposed and the simplified model of DC micro-grids was built. According to the simplified model, the discrete mapping with DC-DC bidirectional converter operating in intermittent mode was built, and the iterative equation and computational formula of feedback factor in stable condition were given. The bifurcation waveform between output voltage and feedback factor was obtained according to iterative equation. Simulation and experiment results show that by increasing the feedback factor, the circuit will work from stable condition to bidirectional point and run into chaos eventually.