Accurate detection technology of the microwave electric field is an important foundation to explore new materials, devices, and electromagnetic effects. In this paper, the design of a microwave electric field detection enhanced by a resonant cavity was proposed and experimentally verified. The simulation results show that the enhancement factor is 3.45 at the position of 3 mm from the square SRR). By combining the experimental system, the actual enhancement factor is 3.31(6), and the corresponding electric field detection sensitivity is increased from 1.02 V/m to 0.30 V/m. The proposed scheme provides certain technical support for the weak microwave electric field detection and the development of the integrated atomic microwave detection unit.