The invention relates to a buffer device. The buffer device comprises a shell, a sliding base, a draw hook and a buffer component. The shell is of a hollow structure. A long-strip-shaped inner cavity is formed in the shell. A sliding groove communicated with the inner cavity is further formed in the shell. The sliding groove extends in the extending direction of the inner cavity. A notch is further formed in the side wall of the sliding groove. The sliding base can slide along the inner cavity. The draw hook comprises a draw hook body, a pin shaft part and a locating boss. The pin shaft part and the locating boss are arranged on the draw hook body in a spaced mode. The draw hook body is in rotatable connection with the sliding base through the pin shaft part. The locating boss is arranged in the sliding groove in a slideable mode. An oblique groove is further formed in the draw hook, and the opening of the oblique groove and the sliding groove are staggered. The buffer component is connected with the sliding base. The draw hook body rotates so that the locating boss can enter the notch from the sliding groove and the opening of the oblique groove and the sliding groove can be consistent in the extending direction. A sliding door can be buffered through the buffer device. Meanwhile, the invention provides a buffer door system using the buffer device.