This application provides a preamble-based locating method and a device. The method includes: A location management function network element receives first indication information from a first network device, where the first indication information is used to indicate a first random access channel resource; sends second indication information to a terminal device, where the second indication information is used to indicate a second random access channel resource, and the second indication information is further used to indicate the terminal device to send a preamble to the first network device and a second network device; sends a location information request to the first network device and each second network device; the location management function network element receives measurement information from both the first network device and each second network device; and the location management function network element determines a location of the terminal device based on the measurement information.