Abstract: The concentration of COD_Mn in water columns was studied in the eight entrances into the Pear River Estuary during February, May, August and November of 2008，Using of pollution index analyzed the pollution status of the concentration of COD_M, and provided basic data and ecological risk basis for the related departments. The results showed that the value of COD_Mn ranged from 1.22 to 3.98 mg/L, with an average of 2.39 mg/L. The spatial distribution showed that the COD_Mn value was low in Modaomen and Honglimen, high in Jitimen and Humen; the temporal sequence was August>February>November>May. According to the second class (COD_Mn≤3 mg/L) of seawater quality standard (Chinese standard), COD_Mn pollution index was relatively low with an average of 0.80, while the exceeding standard rate reached 14.1%. Different estuaries have some degree of pollution, and potential ecological risk of certain organic pollution should not be ignored, strengthening pollution prevention and protection in the Pear River Estuary had a very important significance. [Chinese Fishery Quality and Standards, 2012,):39-43]