Iron-Core coils based electronic current transformer is often used with electrical measuring instrumnts and meters. However, the iron-core coils used as the primary current sensor have nonlinear behavior, and its magnetizing current can be considered as the main error source. Therefore, a nonlinear compensation approach for the iron-core coils based electronic current transformers is proposed in this paper. The approach depends on a linear hardware circuit and a nonlinear numeric control law. Theoretical analysis and experimental results have verified the correctness of the proposed method.