Theoretical analysis of the impact cylinder gap seals show that when the structure size of the impact cylinder is determined,the main factors affecting the leakage are the gap width and the inlet and outlet pressure difference of gap seals.FLUENT software to establish the impact of the use of the cylinder gap seal model to analyze the impact of the cylinder seal gap pressure drop and the gap width of the gap seal leakage of.The results show that the impact of the cylinder under the working pressure range,the impact of the cylinder leakage with increasing inlet pressure increases linearly,when the gap width is small enough,the pressure variations of the amount of leakage is greatly reduced;gap seals and sealing performance mainly due to the gap width of the gap control,the amount of leakage increases as the gap width is increased,but the gap width of the gap width has little effect on the amount of leakage is less than 0.03 mm,so the impact of the cylinder between the piston and cylinder width of the sealing gap should be controlled in 0.03 mm or less.