A method and a system for processing a bearer under an idle mode signaling reduction (ISR) mechanism are provided. The method for processing a bearer under an ISR mechanism includes the following steps. A mobility management network element acquires an access mode of a current network. The mobility management network element notifies a serving gateway (SGW) of the access mode of the current network, so that the SGW processes bearer according to the access mode of the current network. It can be ensured that the access mode of the current network is consistent with the access mode for a policy and charging control (PCC) strategy adopted during a bearing procedure under the ISR mechanism.