An automatic folding automobile tailboard comprises a beam, a lifting arm, a folding support platform and a lifting turnover system, wherein the beam is fixed onto a straight beam at the bottom of anautomobile and connected with the lifting turnover system. The upper end of the lifting arm is connected with the folding support platform, the lower end of the lifting arm is connected with the lifting turnover system, the folding support platform is similarly connected with the lifting turnover system to finish lifting and turnover of the folding support platform, the folding support platform comprises a rear platform and a front platform, the rear platform is connected with the lifting arm, and the front platform can be automatically folded relative to the rear platform. According to the automatic folding automobile tailboard, the front platform can be automatically folded relative to the rear platform connected with the lifting arm, and the unfolded tailboard like a common tailboard isarranged in the rear of the automobile, can be automatically folded and is simple in structure and convenient to operate. A driving cylinder drives a chain and a sprocket, so that the front platformcan be automatically folded and unfolded, cost is reduced, operation is facilitated, and time and manpower are saved.