Abstract: The 3D flow field in the high and low pressure buffer chamber of hydraulic absorber (HA) was studied with computational fluid dynamics software FLUENT on the basis of the experimental results. The results show that the flow resistance of orifices of the high pressure buffer chamber is the major hydraulic resistance part of HA. And flow resistance of orifices increases with piston displacement. Based on the variation curves of flow coefficients of orifices, the calculated buffering displacement curves are in good agreement with the test results, which demonstrates the validity of the 3D flow field numerical analysis model. And the buffering force versus piston displacement curve which characterizes the performance of the HA was obtained. The work of this paper laid foundation for optimal design of the HA.