The invention provides a combined adjustment device for adjusting post insulators and an adjustment method and relates to the technical field of substation electrical equipment installation. The structure of the device comprises a triangular bracket, a horizontal base, laser transmitters, a power supply box, a series compensation platform and the post insulators. Laser rays emitted by a laser transmitter form vertical and horizontal laser faces, and multiple laser transmitters form a plurality of vertical laser faces and a horizontal laser face for adjusting the verticality and horizontal heights of the post insulators. The invention has the advantages that the combined adjustment device can quickly adjust the vertical and horizontal degrees of the post insulators by observing the projection of the laser transmitters, series compensation platform bottom ball heads and post insulator ball sockets are precisely connected by the device and the adjustment method, the connection adjustmenttime of the platform in air is greatly shortened, the installation precision is improved, the operation process is simple, the detection efficiency, the precision are high, and the device and the method can be used by simultaneously adjusting the vertical and horizontal degrees of the multiple post insulators.