The surface of glycerol plasticized thermoplastic starch (TPS) sheets was modified by photocrosslinking under ultra violet (UV) irradiation. Sodium benzoate was selected as photosensitizer and induced onto sheet surface layer by soaking the sample sheets in photosensitizer aqueous solution. The effects of concentration of the photosensitizer aqueous solution, soaking time and moisture content in sheets before UV irradiation on the photocrosslinking were investigated. Water contact angle, moisture absorption, and mechanical properties were measured to characterize the influence of the surface photocrosslinking modification on the properties of TPS sheets. The obtained results showed that the Surface photocrosslinking treatments markedly reduced the water sensitivity of TPS sheets and enhanced their tensile strength and Young's modulus but decreased the elongation at break. (C) 2008, Wiley Periodicals, Inc. J Appl Potym Sci 112: 99-106, 2009