To investigate the effect of fluid dynamics on piston motion in microtexture, based on the software COMSOL Multiphysics, the CFD numerical calculation model was established to analyze the changes of the internal steady-state liquid flow impact force of the texture under the conditions of different texture depth, width and area ratio. After the optimal texture parameters were obtained, the effect of piston velocity on the impact force of steady flow was further analyzed. The results show that the steady-state flow impact first increases and then decreases with the increase of texture depth-diameter ratio or area ratio, when the texture depth-diameter ratio is 0.2 and the area ratio is 49%, the negative flow impact force can be minimized; the increase of piston speed will increase the impact of negative fluid impact, which will hinder the piston from moving at high speed; the existence of surface microtexture changes two relatively parallel surface runner into an ever-changing step runner, and the flow impact force generated in the texture will affect the movement of piston. To simulation analysis the effect law of structural parameters on the steady-state fluid flow impact force is helpful for the follow-up research.