Abstract: The fuzzy entropy of Vague sets should include the unknown and the uncertainty.First，this paper introduces some algebra properties of vague sets and then points out deficiencies of the existing constructional method on entropy of vague sets and gives out a new axiom definition of the fuzzy entropy of vague sets taking into account two factors and presents a new corresponding formula of the fuzzy entropy of vague sets.By proving the theorem and analyzing the example，it is proved that the new formula is more reasonable and the results accord with people’s intuition.