In view of the axiomatic definitions and the structure formulas of intuitionistic fuzzy sets, the defects of current researches which failed to fully reflect the fuzziness of intuitionistic fuzzy sets are introduced detailed respectively. An revised axiomatic definition of intuitionistic entropy is presented and a corresponding formula is structured. Then the intuitionistic fuzzy entropy formulas proposed by former references are discussed and compared with the proposed formula. Example analysis indicates that the proposed entropy measure can fully demonstrate the fuzziness and intuitionism of intuitionistic fuzzy sets.