In order to adapt to the nonlinear characteristics of the electrohydraulic servo system and improve its tracking accuracy to desired position,a position control method for the electrohydraulic servo system based on fractional order controller was proposed.Based on the modeling of the electrohydraulic servo system,the working process was analyzed,and the continuous equation of the flow in the servo valve and the motion equation of the piston were obtained.The firstorder model of the servo valve in the electrohydraulic servo system was established.Through the analysis to the PID controller,a fractional order controller with better robustness was constructed,and adjusting parameters were added to make the dynamic characteristics of the system be better regulated and controlled.Genetic algorithm was used to adjust the parameters of the fractional order controller,so it could better adapt to the nonlinear characteristics of the electrohydraulic servo system,so as to control the electrohydraulic servo system to track the desired position accurately.The designed fractional order controller was used to track the step and sinusoidal desired position trajectory in order to test its control performance.The test results show that the maximum overshoot rate of fractional order controller is reduced by 7.56% and 8.75% respectively when tracking step and sinusoidal desired position trajectories compared with particle swarm optimization controller.It shows that the designed fractional order controller can be used to control the electrohydraulic servo system to track the desired position trajectory better.