The invention discloses a fault air chamber positioning method and device of buses, and the method and device are applied to a GIS system. The GIS system comprises two buses, multiple air chambers arranged in the buses, multiple switches connected in parallel between the two buses and external branches connected with the switches. When a bus fault of the GIS system is positioned, injection currents, collected by a fault oscilloscope, of the different external branches in the fault time as well as current distribution of the switches in the fault time are read; individual fault of each air chamber of the busses is simulated, the current distribution of the switches is calculated by utilizing the injection currents of the external branches in the fault time; and the current distribution of the switches obtained in simulation is compared with the current distribution collected by the fault oscilloscope, and a simulated fault air chamber whose current distribution of the switches is closest to the current distribution collected by the oscilloscope is determined to be the fault air chamber. The range of micro water test for the bus air chambers is reduced, and the fault positioning efficiency is improved.