The present invention relates to an actuator assembly for a base station antenna. The actuator assembly includes a plurality of actuators mounted side by side, a drive shaft, a drive gear configured to be axially movable relative to the drive shaft, and a moving device configured to axially move the drive gear relative to the drive shaft. Each actuator has a driven gear and an actuator element that is in transmission connection with the driven gear. The drive gear is configured for axial movement relative to the drive shaft, so as to engage with or disengage from the driven gear of any one of the actuators and configured to drive the one driven gear in engagement with the drive gear. The actuator assembly has a simple structure, a low height, a favorable PIM performance, and is expandable flexibly.