The invention discloses an efficient heat dissipation type middle gear motor with a centrifugal overrunning double-clutch system, and the motor comprises a housing, a motor shaft, a heat dissipation fan, a rotor assembly, a stator assembly, a planetary speed reduction mechanism assembly, the centrifugal overrunning double-clutch system, and a speed changing chain wheel. The heat dissipation fan isfixed at one side, close to an insulating oil cooling groove, of the motor shaft, the stator assembly and the rotor assembly are arranged in the insulating oil cooling groove, and the centrifugal overrunning double-clutch system comprises a centrifugal clutch, an overrunning clutch inner ring and an overrunning clutch outer ring. The planetary speed reducing mechanism assembly is connected with the overrunning clutch outer ring, and the speed changing chain wheel sleeves the overrunning clutch inner ring. The overrunning clutch transmission is formed when the overrunning clutch outer ring andthe overrunning clutch inner ring are connected in a clamped manner, and centrifugal clutch transmission is formed when the centrifugal clutch and the overrunning clutch inner ring are connected in aclamped manner. According to the present invention, the efficient heat dissipation and zero-magnetic-resistance sliding can be achieved, higher power is obtained, the riding mileage of a whole bicycle is increased, the service life is prolonged, and the riding experience is improved.