Abstract: Aiming at the standardization of moderate indicators with ambiguous optimization directions suffers from simplified quantification process and excessive subjective factors in most comprehensive evaluation models of high arch dam construction scheme, this study proposed the concepts of optimal interval and tolerance interval.By analyzing the distribution characteristics of indicator data and combining with the characteristics of construction simulation calculations, the quartile method and comprehensive weighting method were adopted to determine the subjective and objective interval ranges.The concept of relative membership degree was applied to standardize these intervals, which were then incorporated into the comprehensive evaluation system.The model was verified in the construction simulation scheme selection of the TR double-curved arch dam, and the priority order of alternative schemes was obtained.The results show that this method can more accurately quantify moderate indicators and significantly contribute to improving the calculation accuracy of the multi-attribute decision matrix, and thus obtain more reasonable results of final evaluation model.