Embodiments of this application provide a method for transmitting positioning assistance data and a device. The method includes: receiving, by a network device, at least one positioning assistance data message sent by a positioning server, where the at least one positioning assistance data message is used to carry positioning assistance data; and broadcasting, by the network device, a system message to a terminal device, where the system message is used by the terminal device to obtain the positioning assistance data. According to the embodiments of this application, the network device broadcasts the system message to broadcast the positioning assistance data. In this way, a problem of low efficiency of transmitting existing centralized positioning assistance data can be resolved, and a problem in the prior art that a positioning server needs to perform signaling communication with each terminal device in a unicast transmission scenario can be avoided, thereby reducing signaling overheads.