Abstract: A method for detecting a magnetizing inrush current of a transformer includes the steps of obtaining a difference current for each AC phase of a transformer and calculating, for each AC phase, at least two factors for waveform symmetry recognition, on the basis of the difference currents obtained within one period. For each type of factor, one obtains the maximum value of the three factors corresponding to the three AC phases, to serve as a maximum phase factor of that factor. Based on the maximum phase factor obtained, a waveform symmetry recognition algorithm is used to calculate a corresponding waveform symmetry parameter, and if the waveform symmetry parameter meets a requirement for waveform asymmetry, then it is determined that a magnetizing inrush current has occurred. A device for protecting the transformer is further provided.