The automatic welding machine is designed to weld film products. The automatic welding machine can weld the roof waterproof film, film fabric materials, advertising fabric, lamp box fabric, air materials, canvas covered plastic material, tenting, natatorium, PVC materials, and especially it can weld plastic floors. It is small, light and easy to operate. It has an advance hot air welding system and the welding temperature and speed can be controlled by microcomputer. This machine’s weight can be adjusted to accommodate the different thickness of materials. This function can make the welding result stronger. It also can avoid leakage. This machine is more suited to fast welding of large roofs