The invention discloses a method for safely tripping a gas drilling tool in case of encountering an air layer and belongs to the technical field of tripping in gas drilling. The method comprises the following four steps of: arranging a jet orifice on a sand drain pipeline; circulating a well bore by using nitrogen before tripping; injecting nitrogen into a sand drain pipe and detecting combustible gases on a drilling platform. The invention provides a method for safely tripping of a gas drilling tool encountering an air layer based on the technology of fluid mechanics, which solves the problems that a drill collar passes through a rubber core and the rubber core is scraped off into the bottom of the well. By the method, negative pressure effect can be generated on the sand drain pipeline, the combustible gases overflowing are taken out of the well bottom for exhaustion and combustion and in case of encountering the air layer, the tripping safety is guaranteed.