Abstract: According to the oscillating flow in servocontrolled hydraulic piplines, the actual movement of the transient transition flow was considered. The momentum change of the fluid was analysised in the transient process based on considering its microcompression, and an improved fluid dynamic model of pipeline was proposed. Based on the onedimensional fluid transient theory, the analytical model of fluid transients in hydraulic piplines was carried out by the characteristic method and the finite difference method. The correctness of the simulation was approved by the comparison of calculation data with experiment data .The results show that these models give more reasonable descriptions for water hammer and flow oscillation during servo valve starting process and can provide guidance for designs and experiments of the hydraulic pipe system．