According to the basic principle of flow and flow rate tree model, this paper gave a new defination. the causal relationship tree model, and set up the six system elements into the basic causal relationship tree model. 根据流位流率基本入树模型原理,本文首次提出了因果关系基本入树模型,并建立了关于6个系统要素的因果关系基本入树。