The invention discloses a power transmission line tree barrier risk level evaluation method. The method comprises the steps of step 1, collecting an amplitude I < test > and a frequency f < test > ofa tree barrier discharge pulse; step 2, waveform validity judgment: when the amplitude I < measurement > exceeds a hidden danger discharge amplitude threshold Im1 and the comparison of the section ofdischarge waveform and the power frequency has periodic repeatability, judging the section of discharge waveform as a valid waveform, and enabling the I < measurement > and the f < measurement > whichare judged as the valid waveform to enter historical inventory discharge; step 3, taking an intermediate amplitude weight coefficient kN = Im < 2 >/Im, wherein the intermediate frequency weight coefficient lN is equal to f2/fm, calculating the amplitude I < measurement > and the frequency f < measurement > of the effective pulse according to a formula A < measurement > = kNIm < measurement > + alpha/(lNf < measurement >) to obtain a calculation result A < measurement >, and step 4, carrying out risk level judgment according to the calculation result A < measurement >. The technical problems of many operation steps, high implementation difficulty, miscellaneous and numerous processing information, inconvenience in actual operation and the like in the evaluation process of the power transmission line tree obstacle early warning are solved.