This application provides an antenna downtilt adjustment apparatus, including: a first transmission assembly, a flexible transmission assembly, and a second transmission assembly that are disposed on a mounting plate. The flexible transmission assembly includes a transmission element and a guiding element. The transmission element is in an integrated long strip shape and bendable. One end of the transmission element mates with the first transmission assembly, and the other end of the transmission element mates with the second transmission assembly. The guiding element is secured to the mounting plate, and the guiding element is configured to constrain an extension path of the transmission element on the mounting plate. The first transmission assembly is driven by an antenna information management module, and transmits a force to the second transmission assembly by using the transmission element. The second transmission assembly is configured to drive a phase shifter, to adjust an antenna downtilt.