The invention relates to an electrical linear actuator for a lock, which comprises a motor, a rotating shaft connected with the motor, a spring sleeved on the rotating shaft and a pin arranged on the rotating shaft and also comprises a slider, wherein the slider is provided with a frame capable of receiving the shaft and the spring; grooves for limiting the rotating shaft are formed on a wall; the spring comprises a first winding, end coils and second windings; the first winding is arranged in the middle part of the spring and takes the shape of a cylindrical spiral; the end coils are respectively arranged at both ends of the spring and coaxial with the first winding; the second windings are arranged between the first winding and the end coils, and circumscribed circles of the second windings are convex relative to the first winding; and third windings coaxial with the first winding can be arranged between the second windings and the end coils.