The invention relates to a mounting and fixation structure of an engine air valve. The structure comprises four air valves, a main bracket, an air track, an air track auxiliary bracket, a cylinder cover casing and the like., wherein the air track is connected with the main bracket through the air track auxiliary bracket; the main bracket is fixed on the cylinder cover casing through support webs arranged at both ends; every two of the four air valves are separately arranged on the air track and respectively lean on the support webs arranged at both ends of the main bracket; a position is set aside between the second air valve and the third air valve to arrange a reinforcing plate; and the upper end of the reinforcing plate is connected with the air track auxiliary bracket and the main bracket through bolts, while the lower end is fixed with the cylinder cover casing. On the premise of maintaining engine compactness, position relation with each surrounding part, each mounting position,and the like, the structure increases the rigidity of the mounting and fixation structure and meets the requirements of the integral structure for antivibration capability, intensity and NVH performance.