Abstract:Diatom assemblages on the diatometers were collected from 9 sampling sites ofthe Pearl River at Guangzhou section. Twentydriur genera with 170 diatom taxa wereidentified. Amng them, there were 8 eusaprobic, 84 eurysaprobic and 78 casually saprobictaxa. Conunnity sindlarity cluster analysis showed that the connnnity composition wasmost similar among sites at Yuancun (st3), Xinzao (st8) and shalu0cun (st10) situated atthe middle of Guangzhou section, the commnity sindlarity being reduced gradually at theupper or lower reaches of the river. The diatom assemblage index (DAIpo) values indicatedthat Lianhuashan (st5) and Dasheng (st12) were least polluted which belonged tothe goligosaprobic type, while Huangsha (st2) was most seriously pol1uted and was ofacoosaprobic type- As a site for comparision, Yagang (st1) was also slightly affectedwith pollution, indicating the axiligosaprogic character. The polution of the remaining siteswere between axiligosaprobic and gasesosaprobic. DAIpo had a good negative correlationWith bio1ogical oxygen demand (BOD5) (r=O.86). River pollution index raPId) values ofthe front raPId=56.42) and rear channels (RPId=56.26) of the Guangzhou sectionindicated that the water in these two channels were polluted at a ndddle level.