Abstract: In order to improve the utilization of solar energy and reduce energy loss, the maximum power point tracking (MPPT) is required to adjust the output of PV cells. Firstly, the mathematical model of solar cell is built in this paper. Then a variable step incremental conductance method based on Boost circuit is proposed by considering output characteristic of power versus voltage and current versus voltage for the solar cell and their mathematical relationships. Furthermore, the only one special point value can be calculated simply and rapidly according to the change of external environment, and the special point value is used as adaptive variable step size, which is more reasonable than that of traditional fixed step or variable step size method. In addition, the influence of artificial factors on simulation results is reduced, and the MPPT can be achieved quickly and accurately.