When a unipolar fault occurs on the direct current(DC) side, the DC current of the non-fault pole increases which is caused by the fault pole. In severe cases, commutation failure of the non-fault pole can be caused. When the DC current increases, the existing area-minimum(AMIN) control cannot start an effective emergency trigger at the first time to avoid commutation failure. For the question that the existing strategy cannot accurately calculate real-time commutation margin area, based on theoretical derivation of the existing strategy, the influencing factors that do not achieve the expected effect are analyzed. Then, according to analysis results, improved AMIN control strategy considering DC current change, electric sampling delay compensation and predictive control during commutation is proposed. Finally, based on the PSCAD/EMTDC model which is consistent with actual control and protection procedures, the improved strategy is tested and analyzed. The test results show that the improved strategy can effectively avoid non-fault pole commutation failure caused by the single-pole fault on DC side.