Abstract: Accurate and fast calculation of magnetic material losses under non-sinusoidal excitation is a key link in the optimal design of transformers, motors and other power equipments, especially when containing small biased hysteresis loops. However, there is no efficient and systematic method for calculating the magnetic material losses under such condition. In this paper, based on the point of view that the major loop and its internal biased small loops are independent of each other, the hysteresis and excess loss components of these two different loops were calculated respectively, and the general formula for hysteresis loss computation was derived using the simplified Preisach hysteresis model. To tackle the problem of how to efficiently extract the excess loss statistical parameter, a general formula for its identification was also proposed according to the relation between the simplified Preisach model and excess loss formula of statistical theory of losses（STL）. Consequently, an algorithm for magnetic material losses calculation under non-sinusoidal excitation with the biased minor loops was developed. Using the proposed algorithm, all parameters of the model can be identified with only a small amount of data under the conventional sinusoidal excitation. Finally, the accuracy and practicability of the proposed algorithm were verified by the experiments and simulations.