Abstract： In allusion to the fact when best relative efficiency model and worst relative efficiency model are separately adopted for the Data Envelopment Analysis(DEA) evaluation and ranking, important information will be losed. The definition of interval efficiencies is introduced, which combines two models organically and realizes more reasonable evaluating and ranking on Decision Making Units(DMUs).The DEA models with interval efficiencies are further improved, and the performance of results is analyzed, then reasonable models for calculating interval efficiencies of DMUs are found. In addition, an optimism coefficient of decision maker is introduced for calculating the evaluation index of interval efficiencies. And the analysis results show that worst relative efficiency model is adopted when 0≤β≤05 and best relative efficiency model is adopted when 05≤β≤1. Combining with the numerical example, the evaluation index of interval efficiencies are computed and sensitivity analysis are conducted, and the ranking results indicate that the improved DEA model based interval efficiencies for DMUs ranking is more reasonable.