In order to analyze the influence of grid connected PV power plant on the reliability of power generation system, a multi-state reliability model of PV power plant is established based on the clearness index and fluctuation characteristic, a state division principle of equal interval and equal frequency is proposed,and two state division methods according to different coordinate orders are gave. Then sequential Monte Carlo simulation technology is utilized to assess the reliability of generation system with PV power plant. Simulation results on Roy Billinton test system(RBTS)are in line with measured data demonstrate the rationality of proposed model. Finally, simulation results show that the model with equal frequency division principle and k_DCI/k_VI state division method can get more accurate results in reliability analysis of the generation system with PV power plant.