本文从HMM的基本思想、概念出发，建立了基于网络的HMM异常检测原型。对原型在实际应用环境中产生的问题，提出了对观测对象（数据包头部）进行分段的改进办法，进而建立了具有可操作性的HMM异常检测模型。-From the basic thought and concept of HMM,the article establishes the prototype of HMM anomaly detection based on network.To resolve some problems which produced from the practical application environment,a improved means that partition the observed object to several fields is proposed to improve the prototype,by which　we establish the feasible HMM of anomalous detection based on network.