Embodiments of the present disclosure provide a method for accessing an inter-RAT cell and a related device, and the method includes: sending, by a base station, a first message to a terminal, where the first message is used to instruct the terminal to access an inter-RAT cell, and an LTE cell and the inter-RAT cell are different cells. Beneficial effects are as follows: The first message is sent to the terminal, so that the terminal directly accesses the inter-RAT cell without a need to access the base station. In this way, the terminal does not need to perform a handover procedure, thereby reducing a delay in an access process, effectively ensuring that the terminal can successfully access the inter-RAT cell, and effectively ensuring that a radio access technology new RAT service can be performed between the terminal and a base station of the inter-RAT cell.