The invention discloses a noise identification method in a power line carrier communication fault detection system and belongs to the technical field of electromagnetic compatibility technologies. M sets of measured near field time domain signals of a detected device form an observation signal x(t) used for a matrix, the observation signal x(t) is subjected to independent component analysis, in other words, a separation matrix W is searched for, the y=Wx is made to have highest Gaussianity, after whitening processing is performed, the x(t) is substituted into a Newton iterative formula and separated into M independent near field time domain signals, and waveforms of the M independent near field time domain signals are compared with those of far field time domain signals of the detected device so that signals causing standard exceeding of radiation noise can be determined. The method is simple, efficient and systematized better, frequency points of standard exceeding radiation noise to detected products can be accurately recognized, and therefore a radiation source can be rectified and reformed in a targeted mode, and radiation noise of the radiation source is suppressed.