Abstract: The network based on CSMA/CD protocol has developed as not been solved essentially. In this paper, a theoretical foundation for resolving the uncertainty, is deduced from the angle of mathematics theory. By abstracting the mathematic model of stacking-type network, the structure of stacking-type network is proved to obey the theorem of power rate transition and to be better than the single bus-type network in that it has an exponentially convergent time-sensitivity. Furthermore, through analyzing the network capability of the network throughput and transmission efficiency, the model is evaluated. Finally the theoretical ``however'' of CSMA/CD is summarized and the applications of ``convenience'' of CSMA/CD in the embedded industrial control fields are widened.