The present invention provides a bearer establishment method, a base station, a packet data gateway, and a computer system, where the bearer establishment method includes: receiving a D2D mode indication requested by an AF entity or a proximity service server for a source UE, where the D2D mode indication includes a first D2D connection establishment mode or a second D2D connection establishment mode; and according to the D2D mode indication, when a D2D connection can be established successfully, establishing the D2D connection for the source UE; or when a D2D connection cannot be established successfully, establishing a common connection if the D2D mode indication is the first D2D connection establishment mode, and feeding back a connection establishment failure response to the AF entity or the proximity service server if the D2D mode indication is the second D2D connection establishment mode.