Objective To find out the effects of dry-heat environment on the surface structure of polystyrene. Methods The exposure test of polystyrene( PS) was carried out for one year in Tulufan and Dunhuang. The changes of surface morphology and chemical structures were studied by spectrophotometry, fourier transform infrared ( FTIR) spectroscopy and X-ray photoelectron spectroscopy. Results Cracks on polystyrene surface were observed and yellow index was increased with prolonging exposure time.Organo-functional group C O and O—C O were found during the aging period. Conclusion Photodegradation of polystyrene in dry-heat environment was induced by chain break and increase in carbonyl group.