Circuit nuclear-phase method

The invention belongs to the field of electrical testing and provides a circuit nuclear-phase method comprising the following steps: measuring a circuit induction voltage and determining that the circuit induction voltage is greater than 2,500V; using an induction voltage method or induction current method to carry out the testing, and recording the testing data; and determining the initial end and the terminal end of the circuit in the same phase according to the recorded measuring value. The invention also provides a method for determining the initial end and the terminal end of a circuit inthe same phase by combining a nuclear-phase nine-zone diagram, which is illustrative and rapid and can reduce the error rate.