In this study, the Data Envelopment Analysis (DEA) non-parametrical method was used to assess a set of twenty- one education departments of the Islamic Azad University- Zahedan branch in Iran in 2008-2009 academic years, the results showed eight departments with perfect performance. In DEA models, the efficiency each Decision Making Unit (DMU) is evaluated in best conditions. So such evaluation can be interpreted as optimistic. In this study, in addition to calculation of efficiency through usual method, the efficiency of each educational department is estimated from the pessimistic point of view and with the interval efficiency determination of each educational department, the ranking of units will be dealt with. We also use optimism coefficient as a new method in ranking. One of the most significant advantages of this method is the compatibility and stability of which in ranking, also efficient departments is generally reduced and regarding the optimism coefficient, the manager’s opinion to measure efficiency has been considered as well.