A linear actuator includes a telescoping sleeve (100). The telescoping sleeve (100) includes an inner sleeve (110), an intermediate sleeve (120) sheathing the inner sleeve (110) and an outer sleeve (130) sheathing the intermediate sleeve (120). A base (200) connected to the intermediate sleeve (120); a motor (300) arranged on the base (200); a reduction worm gear (400) pivoted on the base (200) and driven by the motor; a rotor worm (500) pivoted on the base (200) and engaged with the reduction worm gear (400); a rotor worm gear (800) pivoted on the base (200); a stator worm (700) inserted in the rotor worm gear (800) and connected to the outer sleeve (130); and a stator nut (900) connected to the inner sleeve (110) and engaged with the rotor worm (500) are arranged in the telescoping sleeve (100).