The invention relates to field of tramcars, in particular to a buffer type automatic car arrester, and belongs to car sliding-prevention facilities. The buffer type automatic car arrester concretely comprises a main box (1). A pair of front sliding grooves (5) and a pair of rear sliding grooves (6) are correspondingly formed in the two sides of the main box (1); a movable box (4) is installed in the main box (1); a front sliding shaft (7) penetrating the front sliding grooves (5) and a rear sliding shaft (8) penetrating the rear sliding grooves (6) are arranged on the movable box (4); a first baffle plate (13) and a second baffle plate (14) are arranged in the movable box (4), so that the movable box (4) is partitioned into a first compartment (15), a second compartment (16) and a third compartment (17) sequentially. The buffer type automatic car arrester is reasonable in design, the car arrester adopts the mechanical principle, the car arrester can not be started in the circumstance that a tramcar runs at the normal speed, when the downgoing vehicle is out of control, the front axle of the tramcar gets in touch with a dialing plate, so that a braking arresting claw hook is triggered to open, to safely arrest the fast running tramcar.