A method for improving service data flow based charging and a system thereof are disclosed. A CRF may determine, according to input information provided by an AF or TPF, that the charging method for the current data flow service is an online or offline charging method, and provide the TPF with the charging rules with the corresponding mechanism. Moreover, the CRF may provide the TPF with the address information of an OCS or OFCS corresponding to the UE, to enable the TPF to address the corresponding OCS according to the address information of the OCS and trigger the following credit request procedure for the UE, or enable the TPF to address the corresponding OFCS according to address information of the OFCS and send collected charging data information of the UE to the OFCS. Therefore the charging procedure based on the FBC mechanism is more complete and more reasonable.