As the core component of pulse power system, switch plays an important role in pulse forming and power modulation. Usually, the rise time of the pulse generated is determined by the on-off speed of switch and the high-speed switch is vital to the formation of nanosecond short pulses. Therefore, this paper proposes a high-speed SiC-MOSFET package on package structure. The overall layout has no lead or external connection, and has very low parasitic inductance. In this paper, the electromagnetic field simulation research of the proposed package is carried out, and the electromagnetic field distribution of the multi-media interface of the package is revealed during the pulse formation process. The electromagnetic weak link of the package structure is clarified, which provides guidance for further insulation optimization. A dual-pulse test platform was built to compare the dynamic performance of the proposed package-on-package structure switch and the commercial TO-263-7 package switch. The experimental results show that under high current conditions, the proposed packaging improves the turnning off by 48%, the turnning off speed by 50%, the turnning on loss by 54.6%, and the turnning off loss by 62.8%. The experimental results verify the improvement effect of the package-on-package structure on the switch dynamic performance.