Abstract: The set of qualitative belief degrees adopted in qualitative uncertain reasoning is not unique It is found that the approach to comparison of qualitative belief degrees belonging to different sets proposed by Akdag et al has a serious deficiency in consistency with qualitative operation The inconsistency may result in confusion in representation and reasoning about uncertainty Proposed in this paper is a new approach to the comparison of qualitative belief degrees belonging to different sets The qualitative mixed operations of the elements of different sets of qualitative belief degrees are defined The approach is more reasonable in intuitive and consistent with qualitative operation, and in favor of qualitative manipulation of uncertainty under different sets of qualitative belief degrees