A mixed lubrication model of rectangular seal ring was established.The effects of working pressure,piston rod running speed and seal roughness on friction torque and leakage of rectangular seal ring for axial reciprocating were analyzed.The results show that the excessive sealing pressure will damage the seal,which makes the friction force and net leakage increase rapidly.The increase of reciprocating speed will make the friction force increase linearly.The net leakage of linear reciprocating seal is increased with the increase of surface roughness.Using Taguchi experimental design method,experiments were conducted on the operating pressure,running speed and seal roughness of rectangular sealing ring.The optimal combination of parameters was obtained.It is found that the influence degree of each influencing factor on sealing performance is reciprocating speed,roughness and sealing pressure in turn.