Abstract: To address the current situation that residual current protection equipment on transmission lines of low-voltage distribution networks based on TT systems(protection systems where the metal enclosures of electrical equipment are directly grounded) cannot guarantee immediate action after human electrocution, firstly, the in vivo electrocution experiment platform is built, and the electrocution experiment is conducted on the pig epidermis through the power supply with single-phase voltage RMS 220 V and frequency 50 Hz, and the relationship between the electrocution waveform and the electrocution area, the electrocution humidity and the leakage current magnitude at the time of electrocution is studied using the method of control variables to obtain the experimental data; secondly, the experimental data are processed, and the harmonic distortion rate at the moment of touching is calculated using FFT, and the touching waveform envelope is plotted using the cubic Hermite interpolation algorithm to calculate the slope of the envelope at different moments. Finally, the minimum value of harmonic distortion rate and suitable slope are selected, and the simulation platform is built to simulate the human body impedance obtained by fitting the experimental data, and the changes of harmonic distortion rate and peak slope of waveform are used as the basis for judging the electrocution of residual current protection equipment. The feasibility of the proposed criterion is verified.