This application discloses an information transmission method in a communication system. According to the method, a master base station sends a request message to a secondary base station for requesting to transfer one or more flows from the master base station to the secondary base station for transmission to a terminal device. The request message carries one or both of identification information of each flow, and information of a data radio bearer (DRB) associated with each flow. The master base station receives a response message from the secondary base station, indicating whether each of the one or more flows is admitted or rejected by the secondary base station. Based on the identification information of the flows, DRBs are mapped to the flows. QoS management of information transmission is more refined, and requirements of 5G communication systems for QoS management of information transmission in a dual connectivity scenario can be met.