While lots of enterprises use the single point buying model to make profits, few of them noticethe fact that the business complexitieswill finally shift to each pole of the supply chain, therefore, greatly increaseother enterprises'workloads, especially for suppliers. This shows the necessityof supply chain's complexity analysis under the single point buying circumstances. On the basis of the previous research, the frameworkof complexityanalysis for enterprises is built.It is pointed out that the five stages for the complexity analysis of the supply chain are advanced, and an exampleis given to show how the complexitiescaused by single point buying shift betweenbuyers and suppliers. On the basis of data analysis, a general mathematics model which could define the complexity relationships among the entitieson the supply chain is given and the model can help enterprises to Through comparingeach participants on supply chain, their relationship canbe clarified, and the effectof the improvement of the supply chain relationship can be predicted Through systematically comparing process, product line and production, enterprises' inner productiontransformcanbe guided.