Abstract: To make more rational planning and construction of grid-connected new energy system and improve its operational security, an operational risk assessment model of power system, in which the grid-connected wind and photovoltaic (PV) power stations were taken into account, was proposed. On the basis of taking the uncertainty of wind and PV power output, load fluctuation and the real-time status of transmission lines and generators into account, the joint wind and PV power output and the affection of the weather on the outage rate of transmission line were considered to perform the risk assessment more exactly. On the basis of traditional risk index system, where the out-of-limit of voltages, the voltage collapse, the out-of-limit t of active power of transmission lines were taken into account, the sources of risk were more comprehensively considered. Leading in the composite risk indices covering above mentioned indices and combining with analytic hierarchy process (AHP) and entropy weight method, the weight of each index was respectively calculated, thus the obtained results were more objective. Utilizing non-sequential Monte Carlo method the system state was extracted to perform risk assessment. Taking IEEE-14 bus system for example, the influences of the grid-connecting positions of new energy power generations to power grid and the influence of joint power output of wind and PV power generation on power system operational risks are qualitatively analyzed to verify the proposed model and method. The simulation results could be referenced for the risk assessment of grid-connected new energy system represented by wind and PV power generation.