The invention provides a device capable of automatically adjusting intake air temperature. The device comprises a cold air charging pipe, a heating box, a header pipe, a hot air charging pipe, an adjusting plate and a damper, wherein the cold air charging pipe is arranged at one end of the heating box; the hot air charging pipe is arranged at the other end of the heating box; the upper part of theheating box is provided with the header pipe which is used for providing intake air to an engine; the adjusting plate for adjusting the intake air temperature is arranged inside the heating box; theadjusting plate is of a foldable structure; and the damper is arranged below the adjusting plate. According to the device provided by the invention, the intake air temperature is automatically adjusted according to the volume of cold air; the temperature adjusting device adopts a full-mechanical mechanism, electronic control is not needed, and the device is simple in structure, safe and reliable;meanwhile, the temperature can be adjusted to be appropriate; and abrasion, caused by freezing of water at an air charging channel, of engine blades can be effectively reduced.