Online charging method capable of selecting payment by calling party or called party

The invention relates to a charging method of a communication system, in particular to an online charging method capable of selecting of payment by a calling party or a called party. The online charging method comprises communication terminals (1,2), base stations (3,4), a communication exchange center (5) and an online charging system (6), and is characterized in that the answering state of the communication terminal (2) or the communication terminal (1) is provided with three selection modes including hanging-off, answering and paying-answering, and when the paying-answering mode is selected, the communication terminal (2) or the communication terminal (1) sends a charging request signal to an online charging system (OCS) and to a service access control point (SACP) through the base station (2) or the base station (1), and the SACP sends a credit control message (DCC) to the OCS of the user to perform authentication and charging on the called party. 本发明涉及的是种通信系统的计费方法，特别是种可以自选主被叫付费的在线计费方法，它包括通信终端(1、2)，基站(3、4