The invention discloses a measurement method and device for the phase angle during partial discharge of a GIS (Gas Insulated Switchgear). The measurement device comprises a first polar plate, a second polar plate and a low voltage alternating current signal collection and processing device; the first polar plate and a high voltage conductor of the GIS to be detected form high voltage arm capacitance, the first polar plate is arranged outside the GIS to be detected, the first polar plate is arranged opposite to the outer surface of a basin-type insulator of the GIS to be detected; the second polar plate and the first polar plate form low voltage arm capacitance, the second polar plate is positioned on one side, far away from the GIS to be detected, of the first polar plate, and the second polar plate is grounded; the low voltage alternating current signal collection and processing device is connected with the first polar plate, the low voltage alternating current signal collection and processing device is used for collecting voltage signals of the low voltage arm capacitance, and the phase angle during partial discharge of the GIS to be detected is calculated according to the voltage signals. The measurement device and method have the advantage that the measurement process is quick and safe.