In recent years，the photovoltaic（PV）power system has gradually attracted widespread public attention.The rational reliability evaluation of PV power system is very important because of its volatility and intermittence.Based on an analysis of its structure and output characteristics，a six-state reliability model is developed with the energy constraints and the characteristics of system structure of the distributed PV power system taken into account.In addition，an index system is developed for comprehensively evaluating system reliability with respect to the timing，the output，and the system.Test results of an actual PV power system show that the reliability model and index system are rational and feasible and capable of reflecting the operation characteristics of the distributed PV power system，its output，fault characteristics and the reliability of its actual operation.