The invention discloses an installation device for a pole-mounted transformer. The installation device comprises fixed steel channels, sliding steel channels and a hydraulic cylinder, wherein two wire poles which are arranged in parallel are respectively provided with the two fixed steel channels; the two fixed steel channels on each wire pole are symmetrically arranged front to back; one sliding steel channel is respectively connected between the two fixed steel channels at the same sides of the two wire poles; two idler wheels are arranged on the rear side surfaces of the sliding steel channels, and are correspondingly assembled in notches in the two fixed steel channels respectively; the two sliding steel channels are fixedly connected with each other through a connecting rib plate; and the hydraulic cylinder is arranged on the lower end surface of the connecting rib plate. Rising and falling of the two sliding steel channels are realized through actions of the hydraulic cylinder; in addition, the two sliding steel channels roll in the fixed steel channels through the idler wheels arranged on the sliding steel channels, so that the sliding steel channels stably rise or fall; when the transformer is installed, the transformer is firstly put on the two sliding steel channels, and then rising of the transformer can be achieved through the hydraulic cylinder, so that the installation operation is convenient, fast, time-saving and labor-saving.