The utility model relates to a gas detection device for mechanically cleaning a tank and mainly aims at solving the problems that the existing on-line oil storage tank gas detection device can not simultaneously display the detection results of all channels, the detection results are not correct, and elements generate failures easily. The gas detection device for mechanically cleaning the tank is characterized in that sampling-detecting system disks (2) are all arranged inside a storage tank, wherein one end of each sampling-detecting system disk (2) is connected with a sampling pipeline, while the other end of each sampling-detecting system disk (2) is connected with a display alarm system disk (4) through a signal line (3). The gas detection device for mechanically cleaning the tank has the advantages of being correct in detection result, safe and long in service life.