The utility model discloses a gas detection device for a high-tension switch cabinet. The device comprises a gas acquisition device, a gas channel, a gas sensor, a judgment module and a fault category determination module, wherein the gas acquisition device is communicated with the high-tension switch cabinet, and used for extracting gas in the high-tension switch cabinet, and taking the gas as a sample gas; the gas channel is connected with the gas acquisition device; the gas sensor is arranged in the gas channel, and used for carrying out detection on the content of a specific composition in the sample gas; the judgment module is used for judging whether a detection value of the content of the specific composition in the sample gas exceeds a preset value; and the fault category determination module is used for determining the category of a fault occurring in the high-tension switch cabinet and associated with the specific composition. According to the device disclosed by the utility model, by using a principle that when the high-tension switch cabinet has a fault, the compositions of gas in the high-tension switch cabinet have corresponding changes, the fault of the high-tension switch cabinet can be detected through carrying out analysis on the compositions of gas in the high-tension switch cabinet, and the fault detection is not affected by the operation state of the high-tension switch cabinet.