In order to ensure the safety and reliability of the high-level assisted driving system decision-making，a vehicle assisted driving behavior decision-making method based on dynamic driving risk assessment is proposed. Firstly，an obstacle risk assessment model and a virtual lane risk assessment model are established based on the potential field theory，which are used to describe the driving risk caused by dynamic traffic scenarios to the driving vehicle. Secondly，lane change behavior is divided into two stages according to the vehicle lane change process，which are lane change motivation generation and target lane safety decision-making. Further，the risk assessment indicator for lane change scenarios is proposed to formulate safe lane change rules，and the public data set is used to analyze and verify the risk assessment representation capability in lane change scenarios. Then，based on real-time traffic environment information，the driving behavior decision-making method in lane is determined to achieve safe decision-making in various driving scenarios. Finally，the proposed vehicle assisted driving behavior decision-making method is verified on the PreScan/CarSim/Simulink joint simulation platform and real vehicle road test platform. The results show that the proposed risk assessment model and driving behavior decision-making method can accurately identify and evaluate driving risk，and decide the vehicle driving behavior in real time and rationally，which effectively ensures the driving safety of the high-level assisted driving system.