On account of difficulty in finding magnetizing inductance when the transformer is no load and secondary-side voltage and current data are unknown, a method is put forward to solve magnetizing inductance of transformer based on hysteresis loop of dispersed data point. The concrete step is as follows. Firstly, according to the voltage and current sample data point of the primary-side when transformer is no-load, the hysteresis loop of flux linkage and current is found. Then magnetizing inductance is solved through flux linkage and current discrete data point of hysteresis loop. ATP and MATLAB simulation softwares are used to get hysteresis loop and magnetizing inductance. It is concluded that the hysteresis loop and variation of magnetizing inductance are similar to theoretical analysis. So the method can obtain magnetizing inductance when it is no load.