Abstarct: In this thesis, maximum power point tracking at the stand-alone photovoltaic system with Variable resistive load is proposed using a fuzzy controller. This procedure is perform under standard and variable radiation and temperature conditions. Perturbation and observation (P&O) method is also used to track the maximum power point and Compared with the fuzzy method. The results express appropriate performance of the fuzzy controller for maximum power point tracking over P&O method. Furthermore, the particle swarm algorithm is used to optimize the fuzzy membership functions. At the end, by using designed fuzzy controller, the Single phase grid-connected photovoltaic system is implemented. To control of the output current, proportional to the maximum power injected into the grid, the hysteresis method is used for firing the inverter switches.