Embodiments of this application disclose a method, an apparatus, and a system for positioning a terminal device. Location measurement data for a to-be-positioned terminal device is obtained by a terminal-side measurement function entity and/or an access-side measurement function entity, where the location measurement data includes a channel estimation and/or a channel impulse response that are/is obtained based on a corresponding downlink/uplink reference signal. The terminal-side measurement function entity and/or the access-side measurement function entity report/reports the location measurement data to a positioning service function entity in a network, so that the positioning function entity can estimate a location of the terminal device based on the location measurement data, thereby positioning the terminal device and improving positioning accuracy. This technical solution can be applied to both a single-base-station-based positioning environment and a multi-base-station-based positioning environment, to position the terminal device.