The invention relates to a power distribution network cable failure monitoring method based on traveling wave amplitude measure. The method is applied to a neutral point non-effective grounding net with N feeder lines. The method specifically includes the steps of firstly, collecting three-phase initial current traveling wave signals of all the feeder lines; secondly, obtaining zero-modulus initial current traveling wave signals of all the feeder lines; thirdly, obtaining the wavelet modulus maximum m(j) of the zero-modulus initial current traveling waves of all the feeder lines; fourthly, calculating the traveling wave amplitude measure C(j) of all the feeder lines, wherein the definition formula of the traveling wave amplitude measure C(j) is shown as the formula (please see the formula in the specification); fifthly, outputting the small current grounding failure route selection result according to the traveling wave amplitude measure C(j), calculated in the fourth step, of all the feeder lines, wherein the jth feeder line is a faulty feeder line when C(j) is equal to 1, and the jth feeder line is a sound feeder line when C(j) is equal to 0. By means of the method, interference can be reduced, the abnormal running state in the small current grounding mode can be effectively detected, the route where failures exist can be accurately confirmed in time, adverse effects brought by failures can be reduced, and high flexibility is achieved.