In order to ensure that the photovoltaic generation system can reach the maximum power point quickly and operate stably, a Maximum Power Point Tracking (MPPT) controller based on Linear Auto-Disturbance Rejection Control (LADRC) is designed. This paper establishes a mathematical model of photovoltaic cell and DC-DC converter. The first order LADRC is designed to decouple and control, for the purpose of determining the optimal output voltage of the photovoltaic cell array and reducing power oscillation quickly. The design principle of MPPT controller is analyzed. In order to verify the effectiveness and universality of the MPPT controller designed, simulation experiments are carried out by MATLAB/Simulink. Simulation results show that the MPPT controller can improve the tracking speed of the algorithm and reduce the power oscillation significantly. Even if the external environment fluctuates violently, it can still show good control ability and universality. This work is supported by National Natural Science Foundation of China (No.50877053) and Natural Science Foundation of Tianjin (No.09JCYBJC07100).