With the transformation of substation and the gradual transition of substation equipment from periodic maintenance system to state maintenance system in recent years, the overhaul period of some main equipment is gradually extended. And in the power system plays an important role in isolating the power supply, changing the system operation mode, dividing and closing the small load current, reversing the operation of outdoor type isolation switch problems are also significantly increased, directly affecting the supply reliability and security of the system. In recent years, the heating problem of the conductive circuit of outdoor isolation switch has become one of the common defects that trouble the maintenance personnel. Through the problems found in the overhaul of GW5 type outdoor isolator switch in a substation and some improvement measures taken, the author shows that the heating problem of the conductive circuit of the GW5 type outdoor isolator switch has seriously affected the safe, stable and economic operation of the power grid, which must be paid great attention to.