Aiming at the problems of large voltage fluctuation and high local voltage caused by reverse power flow due to large-scale access of wind and solar distributed renewable energy sources to distribution network, basing on the traditional risk assessment theory of distribution network operation, the probability model of distributed generation systems, electric vehicle and load are combined, the risk of high and low voltage are described by using severity function, and a severity function is proposed for high and low nodal voltage. The accident risk assessment in traditional risk assessment theory is replaced by contditional value of risk (CVaR) model. A calculation method of accident impact and loss considering the uncertainty of electric vehicle and load is proposed. The CVaR risk index of voltage fluctuation is established. The estimation method of special functions of distributed generation, charging and discharging power of electric vehicle is proposed. Taking IEEE33 system as an example, the CVAR risk values of voltage fluctuation in normal operation and anticipated fault cases are calculated, which verifies the feasibility and applicability of this method.