介绍了RADIUS协议在GPRS网络Gi接口监测的基本概念和功能，说明RADIUS协议监测模块消息结构，并以此为基础上研究RADIUS协议的解码、重点探讨CDR合成及统计技术、并以RADIUS认证、计费过程为例，详细阐述合成及原理与方法，通过数据采集测试验证了相关理论的有效可行性。-Paper mainly introduced the basic conceptions and functions of RADIUS protocol at Gi interface monitoring in GPRS network, explained the message structure of RADIUS protocol monitoring module.Then researchs RADIUS protocol decoding,and emphasis on CDR synthesis and statistical techniques. As an example of RADIUS authentications and billing processes, this method synthesises the principles and methods detailedly, then proves the theory of effective feasibility by testing data collections.