The invention relates to an automatic airing system for grains. The automatic airing system is characterized by comprising a lifting device, an airing device and a grain collecting device, wherein the lifting device comprises a hydraulic system and a crank rocker mechanism; the airing device comprises airing trays, a connecting frame, a grain collecting chassis and a motor; four layers of the airing trays are arranged on the connecting frame, and the grain collecting chassis is arranged under four layers of the airing trays; the grain collecting device comprises a framework, a conveying belt, driving rollers, driven rollers, a motor, a universal wheel and a walking wheel; and the conveying belt surrounds the driving rollers and the driven rollers to form a rotating circulation loop. The automatic airing system for the grains has the beneficial effects that by virtue of the coordinated cooperation of each device, the automatic conveying, placing, spreading, stirring, airing, collecting and storing of the grains are integrated and mechanized, so that the workforce is liberated, the labor efficiency is increased, and meanwhile, the safety and the sanitation of the grains are maintained; and the automatic airing system has very high social significance.