A quick-releasing linear actuator suitable for electric hospital beds includes a motor, a transmission device, a clutch device and a pulling arm device. With the pulling of the pulling arm of the pulling arm device, a clutch and a clutch base of the clutch device can be disengaged, such that the screw of the transmission device will not be impeded by the worm gear. When a force is exerted to the telescopic rod of the transmission device, the screw can rotate by itself to rapidly lower the telescopic rod, thereby to achieve the rapid releasing of the hospital beds.