Abstract: According to engineering mathematics model of solar photovoltaic cells, a simulation model of photovoltaic cells was established in Matlab, influences of changed light intensity and temperature on output characterstics of the photovoltaic cells were analyzed. In view of problem that it is difficult to get higher tracking accuracy and response speed by use of perturbation and observation method which applied fixed perturbation step, an improved perturbation and observation method based on variable step was proposed. Through simulating photovoltaic cells control system, simulation curves of the two methods of maximum power point tracking were compared. The simulation results show that the photovoltaic cells control system can track maximum power point more quickly and has better stability at maximum power point by use of the improved perturbation and observation method.