The invention discloses a rear protection device of a vehicle. The rear protection device is mounted at the tails of longitudinal beams and comprises a rear bumper, a sliding block, a torsion rod spring, two rear swing arms and a buffering device. The sliding block is transversely arranged between the two longitudinal beams and can slide in the length direction of the longitudinal beams. The torsion rod spring is transversely arranged between the two longitudinal beams, and the two ends of the torsion rod spring are fixedly connected with the sliding blocks. The two rear swing arms are arranged in a spaced mode, the tops of the rear swing arms are fixedly connected with the torsion rod spring, and the bottoms of the rear swing arms are fixedly connected with the back of the rear bumper. The buffering device is arranged on the side, opposite to the rear bumper, of the sliding block in the sliding direction of the sliding block and used for buffering sliding of the sliding block. By means of the torsion rod spring fixed to the longitudinal beams, the torsion rod spring is connected with the rear bumper through the rear swing arms, and due to the fact that that torsion rod spring can carry out certain torsion deformation, the rear bumper connected with the torsion rod spring can rotate around the torsion rod spring. The torsion rod spring is reset through the elastic force of itself after rotating, therefore, the vehicle trafficability characteristic is improved, and reasonable protection on a rear vehicle during tailgating is improved.