Abstract:The original portable hydraulic jack is often applied in earthquake relief work,rescue,hoisting and push,but its volume and single unit weight are big,its support force is not enough,its work efficiency is low,and it is not portable.An ultrahigh pressure manual hydrauliac jack based on ladder piston hand pump and hydraulic double speed cylinder with prefill valve was put forwarded.And the calculation methods for the maximun jack’s load and plunger speed were studied.The practical application shows that its single unit weight is less than 25 kg,its pressure is 63 MPa,its support force is 12×104 N,its plunger speed is 637 mm/min,and it is portable.