The present invention discloses a separation calculating method for a leakage current. The method comprises the following steps: step 1: acquiring an insulated alternating current leakage current signal by using a specific element; step 2: obtaining a second signal sequence by using a first formulation method; step 3: calculating the second signal sequence by using a second specifying method, to obtain a third signal sequence; step 4: obtaining a fourth signal sequence by using a difference between the insulated alternating current leakage current signal and the third signal sequence; determining the fourth signal sequence to obtain a fifth signal sequence, then the fifth signal sequence is a steep pulse component; and step 5: using a difference between the insulated alternating current leakage current signal and the fifth signal sequence as a periodic component. According to the separation calculating method for a leakage current provided by the present invention, a steep pulse component and a periodic component in the alternating current leakage current can be effectively separated, and an application capability of the calculating method is strong.