The present invention relates to derivates of an insulinotropic peptide Exendin-4 and pharmaceutically acceptable salts produced thereof, which are useful for the treatment of type II diabetes. The derivate has the chemical structure as shown below:In which:X represents Leu, Y represents Lys and Z represents Arg-OH.The derivates of this invention may be prepared by synthetic chemical means, and more easily, by the recombinant techniques, which makes it possible to commercial production.