The utility model relates to a drive mechanism for a car power sliding door, which comprises a drive assembly comprising an electric motor, a reducer and an electromagnetic clutch and a transmission mechanism, wherein the transmission mechanism is arranged in a hollow swing arm; one end of the swing arm is sleeved on the output shaft of the drive assembly and bears on a base in a detachable way, and a rotating shaft is arranged on the other end; the transmission mechanism is a synchronous transmission mechanism comprising synchronous pulleys and a synchronous belt, wherein a driving synchronous pulley of the synchronous transmission mechanism is arranged on the output shaft of the drive assembly, and the driven synchronous pulley is arranged on the rotating shaft; a friction plate is arranged inside the sliding door; and a friction pulley which is in contact transmission with the friction plate at all time is arranged on the rotating shaft. By adopting the structure, the transmission mechanism and the drive assembly are integrated in one module, and thereby, the whole drive mechanism has compact structure and small size and is convenient to be installed at corners at the rear of a running board; and the drive mechanism can be not only installed on developing models but also on the existing cars on the basis of not changing body sheet metals, thus having the characteristic of wide applicability.
