This application provides a method for controlling a terminal to use a wireless network, a system, and a related device. The method includes: obtaining, by a network decision device, service information of a terminal, constructing network use indication information, and delivering the network use indication information to a network trigger device; and triggering, by the network trigger device based on the network use indication information, the terminal to use a wireless network corresponding to the service information. According to the method, an operator can assign, based on a service requirement of the operator, the terminal to use a specific wireless network, so that the terminal can use in time a wireless network that is consistent with a requirement of the operator. This helps improve network use efficiency for the operator, and can prevent a service of the terminal from being affected.