Abstract: Objective: The aim of this study was to determinate chemical structure and mass weight of a product suspected as ε- poly- l- lysine from a Stretomyces strain.Methods: The chemical composition of the product was determined by thin layer chromatography( TLC); the UV- VIS wavelength scanning was used to analyze organic groups; the chemical bond among l- lysine residues was analyzed by heteronuclear multiple- bond correlation spectrum( HMBC).Tricine- SDS- PAGE was employed for the analysis of molecular weight.Results: The TLC profile indicated that the product consisted of only lysine; the maximum absorbance was observed at 200 nm,and almost no absorbance at 260~ 280 nm that characteristics of a protein was detected. The HMBC spectrum confirmed that the product from the strain was ε- poly- l- lysine.The ε- poly- l- lysine had an average mass weight of around 3300 u.Conclusion: The product produced by strain GIM8 was ε- poly- l- lysine,and the molecular weight was around3300 u.The combination of the TLC,UV- VIS wavelength scanning,and HMBC can be a suitable approach for the determination of the chemical structure of ε- poly- l- lysine.