An embodiment of the invention provides an aluminum alloy TIG (tungsten inert gas) welding method which solves the problems of rapid heat dissipation and low arc heat concentration of traditional aluminum alloy TIG welding. The welding method includes the steps: reserving a suspension groove below a predicted welding pool area of a welding line to be welded between two workpieces; performing back welding for the welding line to be welded between the two workpieces by TIG welding to form back welding leakage; performing cosmetic welding for the welding line after back welding by TIG welding to form front weld reinforcement.