In high-power direct current transmission projects, the crimped IGBT devices, as the core converter devices, play an important role. In order to adapt to the increasing application scenarios of transmission power, the number of parallel connections of IGBT internal chips is also constantly increasing, which brings about the problem of uneven current distribution inside the device. Although non-invasive methods have achieved great success in monitoring the internal current of circular devices, there is still a lack of effective methods for monitoring the internal current distribution of commonly used square devices. Therefore, this article proposes an internal current monitoring method for square devices based on orthogonal PCB coil groups. This method summarizes the correlation between the internal current distribution and magnetic flux distribution of the device by analyzing the magnetic flux characteristics of the device and coil, and verifies the feasibility of this method in simulation based on this property.