The oil cylinder is used for separating products from die in aluminum extrusion press.Generally,because of exceed temperature of 400 ℃ and long continuous producing time for extrusion products,great heat is generated,result in cylinder body temperature rise,oil deterioration,and seal aging of the oil cylinder under die.A new hydraulic circuit of the oil cylinder was proposed,which had oil circular and cool system.And oil channels were designed on inner measure rod and piston rod,in order to circulate and cool oil timely.So the temperature rise problem of the oil cylinder is thoroughly solved,which can reduce use and maintenance cost,and ensure normal operation of extrusion production line.