In order to facilitate the development of online physics experiment courses and further realize the computer examination of experimental operation, the virtual simulation experiment software of electricity meter refitting is designed and developed on Unity3D platform. The software can be used to adjust the circuit connection and all the actual controllable devices, thus to realize the complete simulation of the experiment process. The virtual instrument has the same appearance, operation steps and precision as the experimental instrument used in teaching. It is equipped with simple UI interface and can help students preview and review the principle and process of experiments on the computer. The design method and parameter selection basis of virtual instrument are described in detail.