Embodiments of the present invention relate to the communication field, and disclose a resource allocation method, apparatus, and system, which solve a problem that the size of resource allocation indication information increases with the increase of the transmission bandwidth, and redundancy of physical layer signaling increases with the increase of the transmission bandwidth. The method includes: allocating time-frequency resources in specific bandwidth to a terminal, where the specific bandwidth is a band less than or equal to system bandwidth; determining the size of resource allocation information according to the specific bandwidth; and sending the resource allocation information to the terminal to indicate the allocated time-frequency resources. The embodiments of the present invention are mainly applied to the process in which the base station allocates time-frequency resources to the terminal.