The invention discloses a barn worm gas and water detection unit with a self protection function. The barn worm gas and water detection unit comprises a control circuit board, a gas collection device,an air path control device, a detection element, an electromagnetic valve control circuit and a pump control circuit. The goal of counting pest attraction density, shooting pest images, and detectingthe phosphoretted hydrogen concentration, carbon dioxide concentration, oxygen concentration and grain pile moisture content of the grain pile can be realized through extracting insect samples and gas samples in a grain pile. The invention also discloses a detection method of the barn worm gas and water detection unit with the self protection function. During the application, the detection flow process can be conveniently controlled; the damage to an oxygen sensor, a carbon dioxide sensor and a temperature and humidity sensor by phosphoretted hydrogen gas can be prevented; the requirements ofthe intelligent warehouse storage can also be met.