The invention provides a gas detection device for benzene series. The gas detection device comprises a box body; the box body is provided with a gas sample injection unit; a gas separating unit, a detecting unit, a data acquisition and processing unit, a control unit and a carrier gas unit are arranged in the box body; the gas separation unit is disposed in a separate separation box; and the gas separation unit includes a ten-way valve disposed inside the separation box. The present invention provides an operation method of the above gas detection device for benzene series. According to the gas detection device, a specific combined chromatographic column is adopted, the ten-way valve which is of a special structure and has a special connection relationship is used in combination, and therefore, the gas detection device is particularly suitable for detecting the benzene series in the atmosphere; and the gas detection device can continuously perform detection and washing in a non-stop manner and can perform repeated detection in a short period of time. With the gas detection device adopted, systematic errors caused by external state changes can be avoided, detection results are morereliable, and accuracy is higher.