For photovoltaic battery array, the maximum power point tracking speed and tracking accuracy is difficult to taking into account simultaneously, proposes a MPPT control algorithm based on bilateral disturbance variable step length, namely two-way variable step perturbation and observation method. Simulates and comparative analyzes the algorithm with the incremental conductance method and the traditional perturbation and observation method. The results show that the algorithm can quickly track the maximum power point and improve the accuracy of 15 ms, and it has better timeliness.