The highspeed onoff valves characteristics of duty ratio and flow was analyzed, the PWM control model based on linear transformation of duty ratio was presented for the dead,nonlinear and saturated zones in the flow control of highspeed onoff valve.The control model could make highspeed onoff valve realize the linear control of average flow. The linear transformation of duty ratio formula was conducted and the PWM control model based on linear transformation of duty ratio was established. Flow control characteristics were analyzed of highspeed onoff valve before and after linear transformation of duty ratio contrastively from angles of simulation and experiment.The analysis results show that when differential pressure is constant, the PWM control model based on linear transformation of duty ratio can make highspeed onoff valve realize the linear control of average flow with the duty ratio of 0~100%.