Switching on no-load transformer in AC system will generate serious inrush current. The injection of this inrush current will lead to the change of fundamental voltage and voltage distortion at AC bus of inverter, which will inevitable influence the commutation process of the inverter. At present, the research is mainly focused on the commutation failure caused by the change of fundamental voltage, while the study of commutation failure resulted by voltage distortion is less. The mechanism of commutation failure created by voltage distortion is analyzed from a perspective of the commutation voltage time area. On this basis, a quick way to evaluate whether the inrush current will bring about commutation failure or not is proposed. This will provide guidance for taking timely and effective actions, which have great sense of making sure the grid operate safely and stably. Finally, the PSCAD/EMTDC simulation results prove the method of evaluation is effective. This work is supported by National Natural Science Foundation of China (No. 51377129).