In the intelligent substation, the process layer network communication is the basis of information sharing and information transmission. To ensure safety and reliability of power system, diagnosing and analyzing process layer network communication is currently a hot research. This paper uses a special smart DAG card, which has simple structure, zero packet loss, high-precision timestamp and other advantages. Then it combines expanded Wireshark analysis software. At last, a network communication fault diagnosis and analysis tool is designed. Meanwhile, it also elaborates three functions with abnormal packet inspection, network status statistics and fault waveform recording. Then this paper displays the strengths and weaknesses of the network communication analysis tool. This design is an integration between fault recording and network traffic records analyzing system. It provides signification in reducing the substation devices and investment, simplifying operation and maintenance.