The invention discloses a directional well and horizontal well drill stem extension tool and a using method thereof, and belongs to the field of a petroleum and natural gas drilling technology. The directional well and horizontal well drill stem extension tool comprises a push end, a creeping end and an energy storage and release structure, wherein the creeping end is located in front of a drilling direction of the push end; the energy storage and release structure is connected between the push end and the creeping end; a sliding limiting structure is arranged between the push end and the creeping end; and the energy storage and release structure is used for compressed energy storage when sliding relatively between the push end and the creeping end under the action of the axial compressive force and for extension energy release when a backing pressure phenomenon occurs or the occurrence tendency exists, thereby pushing the creeping end to slide relative to the push end along a drilling direction. The extension tool is used in combination or used at intervals in drill stems of an inclined or horizontal well section. Specifically, the directional well and horizontal well drill stem extension tool can be arranged between the drill stems, between drill collars and even between other tools, so that the drill stems can be changed into extensible (stretching) drill stems which can automatically store energy and release energy in due time, thereby achieving the purposes of decreasing and even eliminating the backing pressure phenomenon in a drilling process of a directional well and a horizontal well.