The invention relates to an outdoor automatic soldering gun which comprises a gun body, a soldering heating head, an alkane storage device, a combustion nozzle, a power supply, a direct current motor gear speed changing mechanism, a soldering conveying clamp and a soldering wire mounting support. The soldering heating head is arranged at the front end of the gun body, and the alkane storage device and the combustion nozzle are arranged on the upper portion of the gun body; the soldering conveying clamp is arranged on the lower portion of the gun body, and one end of the soldering conveying clamp is installed below the soldering heating head; and the soldering wire mounting support is arranged at the rear end of the gun body and connected with the direct current motor gear speed changing mechanism which is connected with the power supply, and a soldering wire is wound on the soldering wire mounting support. The on-site problems of looseness of circuit joint connection and poor contact are completely solved, and power supply reliability is improved. The cost is low, good economic benefits and high practical value are achieved, and the outdoor automatic soldering gun is suitable for large-scale application and popularization.