A policy control method, a related device and a policy and charging control system in a mobile communication system. The policy control method includes: obtaining description information of two or more sub-flows, wherein the two or more sub-flows belong to a same application; respectively generating policy and charging control PCC rules for the two or more sub-flows according to the description information of the two or more sub-flows; and transmitting at least one generated PCC rule to a PCEF entity or a bearing binding and event report function BBERF entity, so as to perform policy control for the sub-flows by the PCEF entity or the BBERF entity. With the method, device and system according to embodiments of the present invention, a network side entity of the 3GPP network learns that the same application includes multiple sub-flows, and learns the description information of each sub-flow.