This application relates to the field of communications technologies, and discloses a method and an apparatus for transmitting a buffer status report, to help enhance mobility management on a terminal. The method may include: receiving, by a terminal, an instruction message, where the instruction message is used to instruct the terminal to report a BSR, the BSR includes at least one of a first BSR and a second BSR, the first BSR is a BSR corresponding to a first beam link, and the second BSR is a BSR corresponding to a second beam link; and then, reporting, by the terminal, the BSR on the first beam link according to the instruction message.