Automatic sampling and detecting device and method for harmful decomposed gas of underground cable channel

The invention discloses an automatic sampling and detecting device and method for harmful decomposed gas of an underground cable channel, and relates to the technical field of gas detection. The device comprises a gas detection mechanism, the gas detection mechanism is arranged on the inner wall of a cable channel, a gas detection control mechanism is arranged at an inlet of the cable channel, a movable sliding rail is arranged at the top of the inner wall of the cable channel, and a movable pushing assembly is slidably mounted in the movable sliding rail. And a gas sampling box is fixedly mounted at the bottom of the movable pushing assembly. The movable pushing assembly drives the sampling device to move, so that the sampling device slides along the movable sliding rail to a designated place in the cable channel, gas at a certain position is sampled and collected under the condition that the gas detection mechanism at the certain position breaks down, the position is detected in time under the condition tha