Driven by the national energy strategy, the access of new energy such as photovoltaic to the distribution network will increase day by day. It is of great significance to accurately evaluate the risk of voltage beyond limit when photovoltaic is connected to the distribution network. In order to reasonably evaluate the impact of photovoltaic grid connection, a probabilistic load flow method based on maximum entropy principle is proposed to solve the problems of photovoltaic access to distribution network system in this paper. This method has already considered the randomness of photovoltaic output and the fluctuation of load. Furthermore, combined with the utility preference exponential function to characterize voltage over limit severity, a comprehensive model of risk evaluation of voltage beyond limit is constructed. Taking IEEE 33 bus system as an example, it is more accuracy and efficiency in fitting voltage probability density by using the maximum entropy principle than Monte Carlo simulation method. At the same time, the simulation results show that the reasonable selection of access point and access capacity can effectively reduce the risk of voltage beyond limit of the whole distribution network, improve the safe and stable operation ability of the distribution network, and provide a reference for the risk assessment of new energy grid connection in the future.