Quantitatively accurate calculation of the distribution of message and traffic load can not only evaluate the network scheme and provide a quantitative basis for equipment selection, but also for network anomaly monitoring protection criterion and threshold tuning. This paper presents a process bus network message model, including the message transmission path model, equipment input flow calculation model and the traffic load of links calculation model. These models describe the transmission behavior of the messages, and based on the SCD file analysis, the information flow calculation method can be achieved automatically. Finally, it takes the process bus of a typical 110 kV substation network as an example combined with OPNET simulation comparison to verify the validity of the models and methods in this paper.