In order to solve the low control accuracy and tracking error in the maximum power point tracing (MPPT) control in traditional photovoltaic, which was easily occurred under the natural dramatically changing environment, the paper presented a voltage predicting model based on least squares support vector machine (LS-SVM) for the prediction of the voltage of the maximum power output in the PV system, through which the maximum operating point voltage could be predicted, then the reference voltage of constant voltage control method could be modified and MPPT control of the PV system could be eventually realized. Simulation results showed that the model had higher accuracy in prediction, the relative error was less than 004, and the modified control method could guarantee maximum power tracking of the PV system quickly and stably, avoided the phenomenon of tracking error.