The invention relates to an electric meter module mounting device and a mounting method thereof, wherein the electric meter module mounting device comprises a bracket and a jacking mechanism, a firstpositioning mechanism and a gripping mechanism disposed on the bracket. The jacking mechanism is located below the first positioning mechanism and used for lifting the meter tray to the first positioning mechanism. The first positioning mechanism is used for positioning the meter on the meter tray. The gripping mechanism is located above the first positioning mechanism and used for gripping the module to be mounted to a module mounting port for the meter of the meter tray, thereby realizing the accurate mount of the module. The mounting method of the electric meter module mounting device comprises the following steps: S1, the jacking mechanism lifting the meter tray to the first positioning mechanism, and the first positioning mechanism positioning the meter; S2, the gripping mechanism gripping the module; S3, the gripping mechanism mounting the module to the module mounting port of the meter. Preferably, before step S2, the method further comprises a step of the gripping mechanism gripping the module to a second positioning mechanism to complete the positioning.