The edge effect of the electric field in the assembled inertial switch electroforming will disturb the uniform distribution of the power lines between the anode and the cathode. This leads to the problem of poor uniformity of electroforming layer thickness, which prolongates the production cycle. In order to shorten the production cycle of the assembled inertial switch, the megasonic is introduced into the microelectroforming process in this paper. The slider structure has the worst electroforming uniformity in the assembled inertial switch. This paper focuses on how to improve the microelectroforming layer uniformity of the slider structure. Firstly, the current density distribution and layer thickness distribution in the process of electroforming process are simulated by COMSOL finite element analysis software. The simulation results indicate that, compared with the electroforming process without megasonic, the thickness of microstructure obtained by megasonic-assisted electroforming is more uniform. With the increase of megasonic power density, the layer thickness uniformity is better. Secondly, on the basis of simulation, megasonic-assisted electroforming experiment is carried out. Compared with the electroforming process without megasonic, the thickness uniformity of the megasonic-assisted microelectroforming with simultaneous left and right vibration and power density is 2.4 W/cm² is improved by 51.78%. The simulation results are basically consistent with the experimental results. According to the above research results, the assembled inertial switch with the size of 20 mm×20 mm and the height of 900 μm is made by introducing the simultaneous left and right vibration megasonic with the power density of 2.4 W/cm² into the microelectroforming process. The switch meets the design requirement. Compared with the microelectroforming process without megasonic, the manufacturing time of the assembled inertial switch made by megasonic-assisted microelectroforming is reduced by 25%.