The utility model discloses a circuit used for testing admittance and a phase angle of a secondary loop by using a different frequency admittance method. The circuit comprises a secondary loop. One end of the secondary loop is connected to a different frequency signal source, and the other end of the secondary loop is connected to a current test circuit. The two ends of the secondary loop are connected to a voltage measuring circuit. A signal reflecting the current in the secondary loop measured by the current test circuit, and a secondary loop end voltage signal required by the voltage measuring circuit are used as the input signal of an admittance and phase angle test circuit. The admittance and phase angle test circuit outputs the admittance amplitude and the phase amplitude of the secondary loop. The circuit is clear in functions of various parts, and easy to achieve, enables an admittance and phase angle test of the secondary loop. The circuit is advantaged by being few in components, simple in circuit, good in stability, and high in safety.