The invention relates to the field of electric engineering and provides an electric shock moment identification method. The electric shock moment identification method comprises the following steps: S1, carrying out mathematical morphology opening and closing operations on a real-time sampling signal of total leakage current respectively to obtain an opening operation signal and a closing operation signal; S2, calculating differences between a total leakage current signal and the opening operation signal and between the total leakage current signal and the closing operation signal respectively to obtain a positive singularity signal and a negative singularity signal; S3, calculating an absolute value of the sum of the positive singularity signal and the negative singularity signal to obtain an electric shock moment detection signal; S4, comparing the electric shock moment detection signal with a rated value, and taking the moment exceeding the rated value as an electric shock moment. The invention further discloses a residual current protection action criterion utilizing the method. According to the method, the electric shock moment of (a human body or an animal) is quickly identified by a mathematical morphology method, so that the sensitivity and the reliability of a residual current protection device are improved.