Raindrops attached to the surface of grading ring on the power equipments such as insulators and bushings under rainfall and high humidity environment may trigger or intensify corona discharge phenomelons, which have become one of the main sources of surface corona effects in DC power equipment. Mastering the deformation characteristics of raindrops on the conductor′s surface is crucial to reveal the mechanism of corona discharge triggered by raindrops and to guide the anti-corona design of equipment. Starting from the difference in light transmission properties among solid, liquid, and gas, a shadow method optical platform is built to experimentally study the deformation phenomenon of the raindrops under a DC electric field. At the same time, based on the equivalence principle of fluid body force, a fast numerical simulation method of the three-dimensional electrohydrodynamic model is proposed. The deformation mechanism of raindrops is analyzed from experimental and simulation perspectives. The research results show that raindrop images with uniform background grayscale and clear gas-liquid boundaries can be obtained in the constructed optical platform. The proposed numerical method can significantly reduce computational time and ensure accuracy. Research has found that there is a reciprocating deformation phenomenon of raindrops in a DC electric field, similar to the AC electric field. And its deformation rate has a certain periodicity in the time domain. Analysis shows that the reciprocating deformation phenomenon of raindrops comes from the Maxwell stress on the surface of the raindrops perpendicular to the electric field direction. The research results can provide a reference for the study of the electroinduced deformation phenomenon of the raindrops and lay a foundation for further research on the corona discharge mechanism triggered by raindrop deformation.