The present disclosure relates to a phase shifter, which includes: a phase shift circuit board with conductive traces printed thereon; and a phase shift circuit board with conductive traces printed thereon; and a slide device with a first tooth section configured to be driven, wherein movement of the first tooth section drives the slide device to slide on the phase shift circuit board. In addition, the present disclosure further relates to a remote electrical tilt system, which includes an actuator, a transmission mechanism, and at least one phase shifter according to the present disclosure, wherein the actuator is configured to drive the transmission mechanism, and the transmission mechanism engages the first tooth section to drive the slide device to slide on the phase shift circuit board. In addition, the present disclosure also relates to a base station antenna which includes the remote electrical tilt system according to the present disclosure. The base station antenna according to the present disclosure may improve the stability of the transmission of the remote electrical tilt system and increase the space utilization of the remote electrical tilt system.