This application provide an information sending method, and a device and a system. The method includes: creating or updating, by a first device, a network slice instance; sending, by the first device, a first message to a second device, where the first message carries first network slice instance information, the first network slice instance information is first information about the created or updated network slice instance, and the first network slice instance information includes an identifier of the network slice instance; and storing or configuring, by the second device, the first network slice instance information. In the solutions, after creating or updating the network slice instance, the first device may send the information about the created or updated network slice instance to the second device, and the second device may store or configure the information, so as to avoid allocating an improper network slice instance to a terminal.