The invention discloses a car width self-adaption device for a to-be-carried car in a mechanical type parking garage. The device comprises a vehicle loading plate, a side plate is installed on the side, corresponding to a lifting edge plate, of the top of the vehicle loading plate, the side surface of the side plate is symmetrically provided with limiting grooves, limiting shafts are installed inthe limiting grooves, and baffle rods are slidably connected with the middles of the limiting shafts. The device has the advantages that the structure is scientific and reasonable, the use is safe andconvenient, a sliding preventing motor, a screw rod and the baffle rods are arranged so that the baffle rods can be clamped at the bottoms of tires, the shaking towards front and back after a vehicleis parked is reduced, the limiting grooves formed, the limiting shafts are arranged, the two ends of the baffle rods slide in the limiting grooves along the limiting shafts, and therefore the stability in the moving process of the baffle rods is ensured; a stepping motor, a transmission roller, first clamping plates and second clamping plates are arranged, the vehicle can be effectively fixed bythe cooperation of the first and second clamping plates, the left and right displacement of the vehicle is reduced, the vehicle is pushed to move using sliding clamping plates, and the failure of opening the door of the vehicle is avoided.