The invention provides a portable special tool for replacing a 35kV strain insulator string in a live manner. The portable special tool comprises a front clamp, a rear clamp, two worm and worm gear speed reducers, two wire tightening screws, two pull plates and an insulator string bracket, wherein the front clamp comprises a body, a safety pin and two bracket connecting rods fixedly arranged on the body; the rear clamp comprises a clamp body and two hanging rings fixedly arranged on the clamp body; the two worm and worm gear speed reducers are fixedly arranged on the front clamp; the wire tightening screws are in transmission connection with the worm and worm gear speed reducers; one end of each of the two pull plates is fixedly connected with one wire tightening screw, and the other end of each of the two pull plates is fixedly connected with the rear clamp; the insulator string bracket comprises two support rods and a crosspiece; one ends of the two support rods of the insulator string bracket are connected with the bracket connecting rods of the front clamp in an inserted manner, and the other end of the two support rods of the insulator string bracket are arranged on the two hanging rings of the rear clamp. The portable special tool is simple in structure, low in cost, capable of increasing operation efficiency and safety when being used and capable of lowering manpower consumption.