Abstract: Ecological protection is the key to the high-quality development of the Yellow River basin and the evaluation of ecological protection status can help the evaluation object find the direction of improvement. Combined with the ecological characteristics and high-quality development requirements of the Yellow River basin, this paper establishes an ecological protection evaluation index system of the Yellow River basin from four aspects:ecological resources, environmental status, resource utilization and people's livelihood; based on the fuzziness and variability of ecological protection evaluation, this paper studies the ecological protection status of nine provinces in the Yellow River basin with the help of Variable Fuzzy Set. Specifically, this paper defines the standard interval matrix, variable range evaluation interval matrix and M value matrix of each evaluation index, and then reflects the current situation of ecological protection in each province by calculating the degree of comprehensive membership of each index value to each level. The results of this paper show that among the nine provinces, Qinghai, Sichuan and Shaanxi are at an above-average grade of ecological protection, Ningxia at a below-average grade and the rest at an average grade. This finding is basically consistent with the reality that the ecological environment condition of Qinghai and Sichuan is good, and that of the other provinces is at an average level. The results not only provide suggestions for the direction of ecological protection in the nine provinces of the Yellow River basin, but also verify the validity and scientificity of the VFS from the methodological perspective.

Key words: ecological protection evaluation, Variable Fuzzy Set, the Yellow River basin