Abstract: By using restricted equivalence functions,an image thresholding method based on entropy of interval type-2 fuzzy sets is proposed.Firstly,on the basis of the axiom definition,a construction method of entropy measure for interval type-2 fuzzy sets is presented,so that some different formulas are derived to calculate this kind of entropy.Then,through theory justification the optimal threshold can be determined by minimum fuzzy entropy criterion.Finally,experiments demonstrate that,compared with other fuzzy thresholding methods and improved 2-D Otsu's methods,the method can achieve accurate segmentation results and has excellent adaptive capability.