During three years from Aug.1990 to Oct.1993, 14-time investigation were carried out to take 442 samples of organic matter, total nitrogen and total phosphate in the surface layer sediments.The analytical results show that they are characterized by plane distribution.In recent years, the organic matter and total nitrogen increased rapidly, but by no means of total phosphate.By evaluating the surface layer sediments with organic index and organic nitrogen it is showed that the lake is in the state of clear and less clear except East Taihu Lake which has been contaminated heavily by organic matter.