In order to solve the problem that it is difficult to accurately evaluate the frequency response rule and flow output of high speed on-off valve spool in the field of digital hydraulics,a dynamic performance analysis method of high speed on-off valve based on load force function was proposed.The spool dynamics model was derived,the simulation models of electromagnet and the flow field were established,and the no-load dynamic characteristics of the electromagnet were studied.The frequency response and flow output characteristics of the spool were finally obtained by adding the load function and adopting the machine-electric-hydraulic co-simulation method.The simulation results show that the model can reflect the spool frequency response and flow output rule well.The opening time of the high speed on-off valve is 13.9 ms,the closing time is 14.3 ms.When the control frequency is 20 Hz and the duty cycle is from 30% to 70%,the flow modulation linear region is from 1 L/min to 1.9 L/min.With the increase of control frequency,the flow adjustable interval of high speed on-off valve decreases.When the control frequency reaches 40 Hz,the flow rate of the high speed on-off valve is almost unmodulated.