The utility model discloses a pipeline welding auxiliary device. A welding gun connecting driving component of the pipeline welding auxiliary device consists of a base plate, side plates are oppositely disposed on two sides of the base plate, grooved pulleys are arranged on opposite side surfaces of both of the two side plates by rotary shafts, slide bars are disposed on the upper side of the base plate, a first motor is connected with a welding gun connecting block, one end of an upper half cylinder of a cylindrical support component is hinged with one end of a lower half cylinder of the cylindrical support component, the other end of the upper half cylinder is detachably connected with the other end of the lower half cylinder by locking components, an upper semicircular guide plate is overlapped on one side of the upper half cylinder, an upper half gear ring and another upper semicircular guide plate are overlapped on the other side of the upper half cylinder, the lower half cylinder is correspondingly provided with lower semicircular guide plates and a lower half gear ring, an upper tile-shaped block is disposed in the upper half cylinder, a lower tile-shaped block is correspondingly arranged in the lower half cylinder, the grooved pulleys of the welding gun connecting driving component match with guide bosses on the upper semicircular guide plates or the lower semicircular guide plates in a clamped manner, and a gear is meshed with the upper half gear ring or the lower half gear ring. The pipeline welding auxiliary device can assist a welding gun to complete operation of a welding machine, unmanned operation is realized, operation is simple and convenient, the welding machine is high in efficiency and fine in precision, and the pipeline welding auxiliary device is applicable to large-scale popularization and utilization.