Abstract: To build a simple and practical transformer model,two kinds of common transformer models that have such disadvantages as computational complexity,multiple influence factors and inconvenient application are analyzed,and the transformer model based on common information model（CIM） is proposed.The characteristics of proposed model is analyzed from such aspects as structure,impedance calculation and formation of admittance matrix,and this model is compared with the common transformer model,from which it is pointed out that the model can automatically adapt to the regulation of transformer tap,and the simplification parameters calculation is simple,which greatly improves the computational efficiency.In the end,the practical calculation process of parameters is analyzed with example of double-windings on-load tap changer,and the accuracy,simplification and convenience of this model are verified.