The invention discloses a parking and braking mechanism of an automobile gear box, which mainly comprises a parking gear wheel, a parking ratchet, an actuating rod, a slipping spring, a cam slide block, a plurality of support pins, an intermediate moving rod and a positioning track plate, wherein the cam slide block is connected at the front end of the actuating rod and does slipping connection with the rear end of the parking ratchet under the function of precompression force of the slipping spring; the actuating rod is connected on the intermittent moving rod; and the positioning track plate is connected with the intermittent moving rod when in shift P and shift R, and is disconnected from the intermittent moving rod when in shift N and shift D. When in shift P, the parking ratchet is pushed to the parking gear wheel by the driving pin on the positioning track plate through the intermittent moving rod, the actuating rod, the slipping spring and the cam slide block, and then the gear box is braked. By arranging the support pins and the intermittent moving rod, the slipping speed and control precision of the parking and braking mechanism can be enhanced, and the service life of the braking mechanism is prolonged through the slipping connection of linear contact.