Embodiments of this application provide a maximum transmission power determining method, an apparatus, a system, and a storage medium. A network device configures, for a terminal device that works in a DC mode but does not support dynamic power sharing, power information corresponding to a first time unit and power information corresponding to a second time unit when a first radio access technology is used, and correspondingly, the terminal device determines maximum transmission power corresponding to the first time unit and maximum transmission power corresponding to the second time unit.