I n this paper, through the analysis of past transformer load case check product, put forward the high precision design scheme of intelligent transformer load cases of calibration system, this paper discusses the design of intelligent transformer load cases of verification, transformer load calibration system software design, intelligent transformer load cases of checking instrument loop closed loop part design, as well as the upper and lower computer RS232 communication circuit and system and the method of structure design, this paper introduces the design of transformer load cases of calibration system, and discusses the relevant calibration system about the design of the key components.