Embodiments of the present invention disclose a power control method and a terminal device. The terminal device receives configuration information from a base station, where the configuration information includes an uplink power control parameter; estimates, according to the uplink power control parameter, a transmit power that is on an uplink shared channel and that is of a beam set in which a terminal device is located; calculates, according to a maximum transmit power of the terminal device and the transmit power that is on the uplink shared channel and that corresponds to the beam set in which the terminal device is located, a power headroom of the beam set in which the terminal device is located; and generates a power headroom report according to the power headroom of the beam set in which the terminal device is located, and sends the power headroom report to the base station.