The exciting current distortion and significant loss increment of transformer due to DC bias can result in overheating and insulation aging. The dynamic J-A model based on the Jiles-Atherton（J-A） theory and iron loss separate theory are proposed in the way of studying the effects of DC Bias on magnetic properties of ferromagnetic materials. The parameters of model were obtained by an optimization algorithm and loss separation theory

respectively. The accuracy of the model is verified by comparing the simulation results with the measured data. A test system for the electrical steel magnetic performance was built to obtain the loss and magnetic performance data of electrical steel under different DC bias conditions

which were used to analyze the influence of DC bias magnetism on hysteresis loss and dynamic loss. Based on the influence law obtained by analysis

a new method for predicting the hysteresis loop and magnetic loss of ferromagnetic materials under different bias conditions is proposed. Compared the prediction results with the experimental results

it is found that the two are in good agreement and the correctness and effectiveness of the proposed method are verified.