This application provides an antenna and a base station antenna feeder system. The antenna includes a first phase shifter, where the first phase shifter includes a cavity and a phase-shift circuit. The phase-shift circuit is disposed in the cavity. The cavity is connected to a mounting structure, and the mounting structure is configured to connect to a pole. In this solution, the cavity can support the entire antenna using the cavity of the first phase shifter as a frame of the antenna, and by mounting the cavity of the first phase shifter on the pole with the mounting structure.