A linear actuator (1) includes an actuator mechanism (10), a telescopic mechanism (20) and a quick release mechanism (30, 30a). The quick release mechanism (30, 30a) includes a transferring set (31, 31a) connected with the telescopic tube (20), a supporting set (32, 32a) and a braking worm gear (33, 33a) sleeved on the transferring set (31, 31a), a braking worm shaft (34, 34a) connected with the supporting set (32, 32a) and selectively braking the braking worm gear (33, 33a). An elastic pressing assembly (35, 35a) presses elastically on the worm shaft (34, 34a), and the elastic pressing assembly exerted by an external force can adjust the pressing force pressed on the braking worm shaft (34, 34a).