In order to improve the working accuracy of machine tool products,taking the inlet throttle governing circuit as the research object,the study on the reliability and sensitivity of its speed accuracy was carried out.The velocity-load characteristics of inlet throttle governing circuit were analyzed systematically,and the velocity expression of hydraulic cylinder piston could be deduced.The stochastical perturbation theory and fourth-order moment technology were used to establish a model for velocity reliability analysis of inlet throttle governing circuit.Finally,the sensitive parameters affecting the speed accuracy were determined by the reliability sensitivity analysis.The research results show that the valve opening of throttle valve has the greatest influence on the reliability of speed accuracy,so the design should be reduced and the tolerance should be strictly controlled in the design process.