An actuator with a quick-release mechanism includes a base (10); an electric motor (20) including a worm shaft (212); a transmission mechanism (30) including a worm gear assembly (31), a lead screw shaft (32) and a bearing (33); a quick-release mechanism (40) including first and second cylinders (41, 42) attached to the lead screw shaft (32); an elastic member (50) clamped between the worm gear assembly (31) and the second cylinder (42) and a dialing mechanism (60) including a rotating piece (62) pivotally attached to the base (10); and wherein the worm gear assembly (31) including protruding teeth (316); the second cylinder (42) includes teeth slots (424) engaged with the protruding teeth (316) for engaged or disengaged transmission; and the rotating piece (62) includes a dial arm (621) to push the second cylinder (42) to disengage from the worm gear assembly (31) for torque transmission.