The invention relates to a method for assessing occurrence of commutation failure based on the harmonic comprehensive commutation coefficient. The corresponding AC bus voltage of a certain extinctionangle drop moment of operation to the inverter station converter valve is acquired, and the phase offset of the voltage amplitude of each harmonic and the fundamental phase relative to the normal commutation situation and the corresponding leading trigger angle and the extinction angle of the moment under normal operation of the system are obtained after Fourier transform of the AC bus voltage ofthe moment; the harmonic voltage comprehensive influence factor and the harmonic phase comprehensive influence factor are calculated, the two factors are added to obtain the harmonic comprehensive commutation coefficient, and the DC system commutation failure is judged according to the situation of whether the harmonic comprehensive commutation coefficient is greater than the maximum commutation area margin. The calculation method is low in calculation dimension and fast in speed; the method comprehensively considers the harmonic order, the harmonic voltage amplitude and the fundamental offsetcaused by the harmonic waves so that the calculation and judgment result is enabled to be more accurate; and the method is suitable for evaluation of continuous commutation failure.