The invention discloses a method for judging start time of a waveform fault of a fault indicator of a distribution network, and the method comprises the following steps of step 1, reading a waveform file of waveform recording equipment; step 2, taking a sampling point of the waveform file, calculating a time change rate B of the sampling point and the latter point, comparing the time change rate Bwith a threshold value B, and if the time change rate B exceeds the threshold value B, indicating that the sampling point may be the moment of failure; continuing to step 3, and if the time change rate B dose not exceed the threshold value B, proceeding to the next sampling point; and step 3, calculating a half-wave current area integration Iarea of the sampling point, comparing the Iarea with Iset, returning to the step 2 if Iarea is less than Iset, and determining to find the starting point of the fault if Iarea is greater than Iset, thereby solving the problems in the prior art such as theadoption of a method of determining the starting point of a fault based on a sudden change in the slope has large limitations, so that the noise is easily to be misjudged as a fault.