A method and device for sending capability information of a communications device are disclosed. The method includes: determining, by a communications device, information about maximum data transmission bandwidth supported by the communications device; and sending, by the communications device, the information about the maximum data transmission bandwidth supported by the communications device. In the embodiments of the present disclosure, the communications device determines the information about the maximum data transmission bandwidth supported by the communications device and sends the information about the maximum data transmission bandwidth supported by the communications device, so that communications devices supporting different maximum data transmission bandwidth can coexist in a communications system, to implement communication between communications devices supporting different maximum data transmission bandwidth.