When the light intensity and temperature change in photovoltaic system, the conventional maximum power point tracking (MPPT) algorithm was difficult to track the maximum power point quickly and accurately. Aiming at this problem, a fuzzy controller based on improved particle swarm optimization (PSO) was designed. Firstly, according to the characteristics of conventional MPPT algorithm, a fuzzy control algorithm with adjusting factor was designed to rapidly converge to the maximum power point. Then, parameters adaptive PSO was used to dynamically optimize the adjusting factors of the designed fuzzy controller. The simulation results showed that the designed parameters adaptive PSO optimized fuzzy controller could track the maximum power point quickly and accurately, which ensured the dynamic response speed and steady state accuracy of MPPT and improved the work efficiency of photovoltaic system.