The invention discloses a method for diagnosing a fault of GIS (geographic information system) equipment with multicomponent gas on the basis of a PDHID (pulsed discharge helium ionization detector). According to the method, qualitative and quantitative analysis of multicomponent foreign gas in SF6 gas and data storage are completed, whether the GIS equipment has a fault is determined according to test data, and if the GIS equipment has the fault, the type and the degree of the fault are analyzed and judged; whether the fault of the GIS equipment is involved with solid insulation in the GIS equipment is diagnosed, the location and the development trend of the fault are judged, a treatment suggestion for the GIS equipment is proposed, and an GIS equipment diagnosis result is simulated by computer 3D animation. The method is based on the PDHID technology, SF6 gas chromatography, computer software technology and the like are comprehensively applied, the fault of the GIS equipment is studied according to change of concentration of 15 types of foreign gas, fault diagnosis of the GIS equipment is changed from an invisible black box type form to a visible and direct display form, so that judgment of the equipment fault is more facilitated, and timely treatment is facilitated.