The utility model discloses an installation tool of an overhead line fault indicator. A support rack comprises two supports which are provided with opening ends disposed on an insulated cup body and which are symmetrically disposed, the two supports are separately hinged to the insulated cup body, the middle and upper parts of the two supports are provided with a connecting piece, the connecting piece is located on a plane which intersects with a plane where the two supports are located, the two supports together with the connecting piece can swing around hinge points of the two supports, the upper parts of the two supports are respectively provided with a vertically distributed positioning convex block, the two positioning convex blocks and the connecting piece are respectively located on two sides of the plane where the two supports are located, and the distance between the outer surfaces of the two positioning convex blocks is equal to or less than the distance between the two support racks of the fault indicator. The supports with the positioning convex blocks are additionally disposed on an insulated cup body of an installation tool of an existing fault indicator, so precise positioning of a V-shaped clamping groove and a pull pin can be performed, precise return of the V-shaped clamping groove and the pull pin can also be promoted, return of the pull pin is convenient, and then the installation success rate of the fault indicator is improved.