The invention relates to a small-size imaging device, comprising a lens assembly, an image sensor, an actuator and a spring; wherein the actuator is used for adjusting the position of the lens assembly and composed of at least one magnet and at least one coil; the spring is arranged between the at least one magnet and at least one coil; a first part of the lens assembly is arranged in a center cavity of the actuator and a second part of the lens assembly is arranged between the center cavity of the actuator and the image sensor; the radial size of the first part is smaller than the radial size of the second part; at least one magnet is connected with the first part and at least one part of the actuator is connected with the image sensor.