The life of the hydraulic pump is affected by many factors. According to the statistical information of failure of the main hydraulic pump of an aircraft, we apply the reliability engineering theory to calculate and analyze its service life. As known in calculation, the service life of hydraulic pump conforms to Weibull distribution, and there is no the useful life period. The basic reasons resulting in the decline in the service life of the pump are the higher work pressure, the poor work condition and serious hydraulic system pollution. Furthermore, several measures for use and maintenance are given.