Disclosed is a ground-wall insulation aging monitoring and locating method for a converter transformer. A neutral lead of three-phase windings on a valve side of a converter transformer is adjusted, an insulation leakage current of a certain phase winding on the valve side before aging is measured, a common-mode component and a differential-mode component in the insulation leakage current before aging are extracted, and a common-mode equivalent capacitance and a differential-mode equivalent capacitance before aging are calculated; a common-mode equivalent capacitance and a differential-mode equivalent capacitance after aging are calculated in the same way.