The present disclosure relates to a liftable luggage carrier on a car roof. The liftable luggage carrier on a car roof includes: sliding frames, at least two sliding frames are arranged, the sliding frames are fixed on the car roof, and limiting baffles and several locking holes are provided on the sliding frames; sliding seats are slidably installed on the sliding frames, one or two sliding seats are arranged on the sliding frames, and the sliding seats are positioned on two sides of the limiting baffles respectively under the situation that two sliding seats are arranged; positioning devices are installed on the sliding seats to be used for positioning the sliding seats when the sliding seats slide to a position above the locking holes.