As the core power component of hydraulic system,the energy conversion efficiency of hydraulic piston pump largely determines the performance and reliability of the whole hydraulic system.At present,most of the energy conversion efficiency models used are deterministic numerical models,which do not consider the influence of parameter randomness,and can not truly reflect the actual operation state of piston pump.The overall efficiency modeling method of the piston pump based on Kriging model was proposed.Taking the overall efficiency of the piston pump as the reliability failure criterion,the reliability and reliability sensitivity for the overall efficiency of the piston pump were analyzed by the advanced first order and second moment method and the Monte-Carlo numerical simulation method,respectively.The results show that the overall efficiency model simulated by the Kriging model with a small number of samples has a higher accuracy,which can obtain the comprehensive overall efficiency characteristics of the piston pump.The operating conditions have a great influence on the reliability sensitivity for the overall efficiency of the piston pump,and the sensitivity varies greatly under different operating conditions.The presented method can be extended to the establishment of overall efficiency models and reliability sensitivity analysis of other hydraulic pumps.