Abstract: Under the partially shaded condition(PSC), the power curve of the photovoltaic array has multiple peaks. The traditional tracking methods are effective under uniform illumination condition(UIC), but cannot track the global peak(GP) under PSC. In order to track GP quickly and effectively under uniform illumination condition and partially shaded condition, a GP tracking algorithm based on variable step incremental conductance(INC) method is proposed. The main body of the algorithm consists of four steps, which are executed circularly to find the global peak point. In order to improve the tracking accuracy, the algorithm uses an INC algorithm with variable step size to reduce the disturbance step size near the local peak point. In order to reduce the tracking time, the algorithm uses two kinds of perturbation step. Especially in step 2 and step 3, the tracking speed is accelerated by adopting a larger disturbance step size. Finally, the effectiveness of the proposed algorithm is verified by building a model in Matlab. Simulation results show that the proposed method is faster, more accurate and more efficient than the traditional INC global method.