The invention relates to a grounding method for a shielding chamber of protective equipment in a transformer substation. The method comprises the following steps: firstly, the aim to ground a protective chamber is analyzed; after the aim is known, the influences of the different grounding modes on reduction of electromagnetic disturbance are compared; and the reasonable grounding modes and the realization methods are determined through tests, investigations, and accumulation of operating experience. The grounding method is very accurate, and can provide basis and reference for designing the grounding of the protective chamber of secondary units in high-voltage transformer substations in the future.