Abstract: In the Yellow River Conservancy Technical Institute MPPT control of photovoltaic power systems，it makes the photovoltaic battery has the highest utilization rate and improves the efficiency of power generation.It analyzes the basic principle and advantages and disadvantages of DOM(Disturbance Observation Method)，and proposes an improved algorithm.The setting perturbation step is relatively large，when the working point goes away from the range of MPP；the setting step is relatively small，when the working point goes close to the range of MPP.Improved algorithm is verified through simulation experiments，it is concluded that when external conditions change drastically，the improved algorithm can not only reduce the loss of power，but also can improve dynamic response and stability of the system，then gets the expected control effect.