A similar ACE inhibitory peptides YYAAY were synthesized by solid phase synthesis. The crude peptide product were separated and analyzed by RP-HPLC, then characterized by ESI-MS. The interaction of YYAAY with DNA had been examined through utilizing fluorescence and ultraviolet spectroscopy and viscosity method. Result showed that the absorption spectra of DNA were decreased with increasing the concentration of YYAAY. When the concentration of DNA increased, the absorption spectra of YYAAY presented hyperchromic effect, and the fluorescence of YYAAY had quenching effect. The viscosity of DNA-YYAAY was decreased too with increasing the concentration of YYAAY. The experimental results revealed that YYAAY inserted in DNA with the mode of the “partial” (or the “nonclassical”). According to the Scatchard equation, the binding constant of YYAAY with DNA was calculated to be K=2.7×105 L·mol-1