A method for monitoring a service usage amount, comprising: determining, according to one of quintuple information, protocol information, and URL information in received service request information, whether the service request information is the same as specified service stream information in multiple session level service monitoring tasks; wherein each session level service monitoring task comprises a session level service monitoring class identity, a monitoring task identity, and the specified service stream information; the monitoring class identity indicates that the monitoring task is used to monitor a usage amount of a specified service stream in a session; when determining that the service request information is the same as the specified service stream information in the multiple session level service monitoring tasks, accumulating a usage amount of the service stream in the multiple session level service monitoring tasks; and reporting the monitoring task identity and the accumulated usage amount of the service stream in the session level service monitoring task to a Policy Charging Rules Function, PCRF; before determining whether the service request information is the same as specified service stream information in each session level service monitoring task, further comprising: sending a session establishment request to the Policy Charging Rules Function; and receiving each of the session level service monitoring tasks sent by the Policy Charging Rules Function; wherein the receiving each of the session level service monitoring tasks in the session sent by the PCRF is specifically: receiving monitoring class identities and monitoring task identities of the session level service monitoring tasks sent by the Policy Charging Rules Function through a Gx+ interface, and receiving specified service stream information and monitoring task identities of each session level service monitoring task sent by the Policy Charging Rules Function through a service stream information synchronization interface. determining, according to one of quintuple information, protocol information, and URL information in received service request information, whether the service request information is the same as specified service stream information in multiple session level service monitoring tasks; wherein each session level service monitoring task comprises a session level service monitoring class identity, a monitoring task identity, and the specified service stream information; the monitoring class identity indicates that the monitoring task is used to monitor a usage amount of a specified service stream in a session; when determining that the service request information is the same as the specified service stream information in the multiple session level service monitoring tasks, accumulating a usage amount of the service stream in the multiple session level service monitoring tasks; and reporting the monitoring task identity and the accumulated usage amount of the service stream in the session level service monitoring task to a Policy Charging Rules Function, PCRF; before determining whether the service request information is the same as specified service stream information in each session level service monitoring task, further comprising: sending a session establishment request to the Policy Charging Rules Function; and receiving each of the session level service monitoring tasks sent by the Policy Charging Rules Function; wherein the receiving each of the session level service monitoring tasks in the session sent by the PCRF is specifically: receiving monitoring class identities and monitoring task identities of the session level service monitoring tasks sent by the Policy Charging Rules Function through a Gx+ interface, and receiving specified service stream information and monitoring task identities of each session level service monitoring task sent by the Policy Charging Rules Function through a service stream information synchronization interface. sending a session establishment request to the Policy Charging Rules Function; and receiving each of the session level service monitoring tasks sent by the Policy Charging Rules Function; wherein the receiving each of the session level service monitoring tasks in the session sent by the PCRF is specifically: receiving monitoring class identities and monitoring task identities of the session level service monitoring tasks sent by the Policy Charging Rules Function through a Gx+ interface, and receiving specified service stream information and monitoring task identities of each session level service monitoring task sent by the Policy Charging Rules Function through a service stream information synchronization interface. receiving monitoring class identities and monitoring task identities of the session level service monitoring tasks sent by the Policy Charging Rules Function through a Gx+ interface, and receiving specified service stream information and monitoring task identities of each session level service monitoring task sent by the Policy Charging Rules Function through a service stream information synchronization interface.