Movements of a cam mechanism working in transformer oil environment affects performances of an on-load tap-changer used in ultra-high voltage direct current project, which needs a suitable method to analysis the cam mechanism motion in transformer oil environment. In this paper, a performance analysis method is introduced for the on-load tap-changer cam mechanism in transformer oil environment. A simulation platform that can realize different motion simulation analysis of the cam mechanism under transformer oil environment is established using Particleworks software, and an experimental platform is built to assist in simulation parameter setting. According to experimental results and theoretical calculations, calculation results of simulation platform can better fit physical situation by adjusting simulation setting parameters. It provides a basis for performance analysis of key structures on the on-load tap-changer.