An electromagnetic transient model of transformer is proposed based on the J-A（Jiles-Atherton）model simulating its hysteresis characteristics. Differentiation is used to obtain the discrete model. The J-A hysteresis model is implemented by injecting extra current source to the transformer model. By thorough analysis of the numerical characteristics of the J-A model in different simulation step length，the computation efficiency is improved through the use of multi-rate simulation schema. By comparing multiple test cases，the proposed model is validated. The improvement of efficiency is also verified through the comparison of consumed times. It provides an efficient and reliable implementation method for transformer hysteresis simulation based on J-A model in electromagnetic transient simulation programs.