In order to study the relationship between the instantaneous speed fluctuation of hydraulic motor and the hydraulic system efficiency under stationary condition,the experimental verification method was adopted.In the variable speed hydraulic test bench,by changing the motor speed through LabVIEW software and setting the magnetic powder brake load voltage to simulate working condition,the change curves of the hydraulic motor instantaneous speed fluctuations and the hydraulic system efficiency under the constant rotational speed changing load and constant load changing rotational speed stable working conditions were collected and analyzed.The experimental results show that the hydraulic motor instantaneous speed fluctuation and hydraulic system efficiency is relevant.The higher the speed is,the smaller the speed fluctuations of the hydraulic motor is and the higher the efficiency of the hydraulic system is.On the other hand,the change is opposite.Under the stationary condition of constant load changing rotational speed,with the increase of the motor speed,the hydraulic motor speed fluctuation is reduced and the efficiency of the hydraulic system is increased,the efficiency is significantly increased in low speed and slowly increased in high speed;under the stationary condition of constant rotational speed changing load,with the increase of the pressure,the hydraulic motor speed fluctuation is increased and the efficiency of the hydraulic system is reduced.The research results provide reference for choosing the appropriate range of the hydraulic motor speed and load,decreasing the instantaneous speed fluctuation of the hydraulic motor and improving the efficiency of hydraulic system under stationary conditions.