Instantaneous flow is a time-varying function that can be considered flow pulsation added to the average flow rate. Pressure pulsation is caused by flow pulsation that may affect the working performance of a hydraulic system, then cause structural vibration, radiation noise, and fatigue damage to components of the hydraulic system. It is thus important to restrain vibration in the design of the hydraulic plunger pump. The paper puts forth a model of flow pulsation and pressure pulsation function and simulates the curve using Fourier series based on the operating performance of hydraulic pump, for the excitation function using in noise analysis of hydraulic pump system, in order to solve the problem of noise analysis of the hydraulic pump system and to provide pulsating description for the response of the noise and vibration of hydraulic piston pump.