The invention relates to a GIS apparatus with a discharge observation window and belongs to the technical field of online high-voltage switch monitoring. According to the GIS apparatus, the observation window is designed on the side surface or the top surface of a GIS cavity, and the diameter of the observation window and the angle of inclination of the axis of the window to ground can be determined according to the generatrix length and the angle of inclination of the section of a basin-type insulator cone in the GIS cavity. As the observation window is arranged on the GIS cavity, the position of partial discharge, the arc shape, the defect type and the like can be visually seen, and the problem of failure in visually knowing the optical phenomena in the development process of the GIS partial discharge process is solved; meanwhile, in combination with other partial discharge diagnosis methods, the partial discharge information is diagnosed comprehensively; the methods are complementary to each other for verification to make up for misjudgment possibly caused by one single method.