The edge groove structure of the rotary valve has a significant impact on the assist characteristics of the hydraulic power steering gear,but there is little research on the design method of the edge groove structure.Based on the structure and working principle of the rotary valve,a mathematical model and AMESim simulation model for the flow area of the rotary valve port of the hydraulic power steering gear were established.The reliability of the model was verified by comparing it with experimental results.Based on the design objective of the assist characteristics of the new product,a curve fitting based edge groove design method was proposed.Based on the design objective of the assist characteristics,the parameters in the analytical formula of the edge groove curve were solved using MATLAB software.The simulation results show that the designed edge groove structure can meet the design requirements,the effectiveness of the design method is validated,and it provides a reference for the optimization design of hydraulic power steering gear.