Objective To study the calculation of the cost consumption index adjusted with major diagnostic classification (MDC), for optimal use of DRGs index in hospital performance evaluation. Methods The adjustment method of CMI value in DRGs index system was used as reference, and we compared the different cost consumption indexes(both MDC adjusted and non-adjusted) of two hospitals(S and Y) in Guangdong province. Then we compared the different rankings of 82 tertiary general hospitals in the province before and after the adjustment. Results The cost consumption index of S hospital was higher than that of Y hospital by the non-adjusted method (1.30 >1.28). But as calculated by the adjusted method,the index of S hospital was significantly lower than Y hospital (1.31 <1.38). The rankings of these 82 hospitals also showed major changes,which prove that the cost consumption index, the same as CMI,will be affected by MDC cases makeup.Conclusions The MDC adjusted cost consumption index, when applied to hospital performance evaluation, renders more stable and reasonable results. This is an evidence that the adjusted cost consumption index is of great practical value in hospital performance evaluation.