Considering that geomagnetically induced current (GIC) has low frequency, it has been approximately equivalent to the imbalance current induced by high voltage direct current (HVDC). However, compared with the HVDC-type DC bias, the GIC-type DC bias has significant randomness and time-varying, so it is not reasonable to simply treat the two as completely equivalent, and they should be distinguished in specific scenarios. For this reason, first, the differences in the induced causes and characteristics of the two types of DC biases are analyzed theoretically. Second, by studying the adverse effects of DC magnetic bias on transformer body and current transformer, the differences of the influences of the two types of DC magnetic bias on primary/secondary equipment of power grid are further explored to provide effective reference for subsequent magnetic bias treatment. Finally, an equivalent simulation model is built based on the PSCAD/EMTDC simulation platform, and the correctness of the theoretical analysis is verified by simulation. This work is supported by the General Project of National Natural Science Foundation of China (No. 51877088).