In thi spaper, the specific application of key words spotting used in the network monitoring is studied, and the keywords spotting is emphasized. The whole monitoring system is divided into two mod-ules:network monitoring and keywords spotting. In the part of net-work monitoring, this paper adopts a method which is based on ARP spoofing technology to monitor the users data, and to obtain the original audio streams. In the part of keywords spotting, the extrac-tion methods of PLP (one of the main characteristic parameters) is studied, and improved feature parameters -PMOCC are put forward. Meanwhile, in order to accurately detect syllable, the paper compares the double-threshold method with variance of frequency band method, and use the latter to carry out endpoint detection. Finally, recognition module is built by HMM, and identification results are contrasted under Matlab environment. From the experiment results, a better solution for the appication of key wards recagaition technology in network monitoring is found.