A method for transmitting a signal of a medium access control sublayer in a mobile communication system which has mobile and base stations for providing a bearer service. A bearer service profile type is decided according to a bearer service combination type of the bearer service for the provision of the bearer service. A transport format indicator is set according to the decided bearer service profile type, and a transport format combination indicator is appended to a dedicated physical control channel. The most efficient data is transmitted on the basis of a service type and a measured radio environment result. Therefore, a data frame format most suitable to a channel environment can be produced, thereby providing the best service.