Abstract: The effects of light,solution medium,heavy metal ions,and typical photosensitizer under aquatic environment on the photo-degradation of cetyltrimethylammonium bromide (CTAB) ,which was selected as the typical cationic surfactant,were investigated.The results showed that:1) The degradation rate of CTAB under the UV light was the fastest compared to the rate under natural light and dark conditions,its degradability is 37.02% after 20 min,and almost no reaction in the dark.2) The degradability of CTAB in de-ionized water (31.49%) was faster than that of the artificial sea water (19.04%) .3) Different heavy metal ions have different effects on the degradation of CTAB.The degradability of CTAB was 29.33% and 24.54% after 20 min photo-degradation under the condition of 0.1 mg/L Zn2+ and Cu2+,respectively.4) The degradability of CTAB was 36.92% and 22.54% after 20 min,when 0.1 mg/L acetone was chosen as the photosensitizer in de-ionized water and artificial seawater medium,respectively.The results may be used as effective reference for the aquatic management of the cationic surfactants.