Embodiments of the present application provide a method for determining a transmission time interval, a base station, and a radio network controller. A base station receives uplink data sent from a user equipment in an idle state or a cell forward access channel state on an enhanced dedicated transmission channel. The base station determines a transmission time interval (TTI) used by the user equipment for sending the uplink data, and sends the uplink data and a transmission time interval indicator in an enhanced dedicated transmission channel data frame to a radio network controller. The radio network controller acquires the TTI, thereby ensuring that the radio network controller selects and configures an appropriate TTI for the user equipment when the user equipment transits from the Cell_FACH state to the Cell_DCH state.