摘要：Set pair analysis (SPA) is a method for the application on analysis of risks and project decision evaluation.This method combines qualitative analysis and quantitative analysis. The previous SPA study only focusedon three ranks evaluation. This paper presents an improved SPA method utilizing original relation degreemalleability of SPA, and extends it to five ranks evaluation. The improved method can depict identity,discrepancy and contrary in more detail. In addition, this study combines fuzzy comprehensive evaluationmethod to evaluate four main factors of surface water environment, instead of the discussion of i + , i – , j + , j –coefficient. It not only obtains evaluation result but also obtains probability distribution of each rank. In thispaper, we apply the method to factual example and compare the results with synthesis index method, andgray associated analysis method. We conclude that the improved method can represent the true state of theobject with extensive engineering application value.
