The present invention relates to a method and a device for fast assessment of whether a magnetizing rush current causes commutation failure of a HVDC or not. Conditions required by commutation successare provided in a condition of distortion of an inverter AC busbar voltage by starting from analyzing the influence mechanism of the harmonic wave for the commutation process; a concept of a commutation margin is defined, factor bad for commutation are calculated such as boundary values of the decreasing of a harmonic voltage and a fundamental voltage which all supplement the current research gaps for the commutation failure caused by the harmonic waves and have a certain theoretical significance. Besides, assessment indicators which can represent the fundamental voltage change and the voltage distortion are provided, a threshold value used for determination of whether the commutation failure is generated or not by employing the indicators is calculated, a method for fast determination ofclosing and space-variant has risk of commutation failure or not is provided, and guidance is given to adopt timely and effective measures, and the method and the device have a certain practical value.