本文利用流体流方法计算了实时媒体流在缓冲区中的时延概率分布函数 ,给出了时延约束下实时媒体流的等效带宽的表达式。讨论了相关参数对等效带宽的影响。进行了仿真分析和验证。该表达式计算简单 ,便于实时带宽估计和控制。 In this paper, we use the fluid flow method to calculate the probability distribution function of real-time media flow in the buffer, and give the expression of the equivalent bandwidth of the real-time media flow under the time-delay constraint. The effect of the relevant parameters on the equivalent bandwidth is discussed. Have carried on the simulation analysis and the verification. This expression is computationally simple to facilitate real-time bandwidth estimation and control.