Abstract: The relationships between organism and its surroundings have been widely adopted to evaluate the health of eco-system. Through the analysis of the size-fractionated phytoplankton in black and feculent water, it discussed the effect of bioremediation on all size-fractionated phytoplankton and the relationship of all size-fractionated chlorophyll-α with envi-ronmental factors to bioremediation, so as to provide biological proof for illustrating the efficiency of measures taken for the bioremediation.Comprehensive measures concerning ecology including the way of adding bioenergizer, biologic algaecide, effective microbe into water, and planting macrophyte are adopted. Group A is the contrast group, does not use any measures; Group B, C, D, E, F and G are test groups. Group B add photosynthetic bacteria and nitrifying bacteria; Group C add photosynthetic bacteria nitrifying bacteria and oxygen strengthen; Group D add photosynthetic bacteria nitrifying bacteria bioenergizer and oxygen strengthen; Group E add photosynthetic bacteria nitrifying bacteria bioenergizer plant Eichhornia crassipes and oxygen strengthen; Group F add photosynthetic bacteria nitrifying bacteria bioenergizer and plant Eichhornia crassipes; Group G add bioenergizer and oxygen strengthen. Beforehand, background was sampled twice on 28th of August in 2002. The experiment began from August 29, 2002. And after the engineering project, samples for water quality analyses were collected on the 29th and 31st of August, the 3rd, 6th, 9th, 12th and 17th of September respectively. Water samples for phytoplankton analyses were collected with length Niskin bottles (for a total final volume of 10L). The samples were divided into Pico (0.2-2.0 μm), Ultra (0.2-5 μm), Nano (2-20 μm) and Net (20-200 μm) size fractions by filtration. Chlorophyll-a was determined by spectrophotometry following the methods proposed by Lorenzen on the 9th, 12th and 17th of September in 2002 respectively. Within the periods of this survey, both of CODcr and BOD5 lowered after bioremediation and the effect of cleansing were very significantly in group C, D and E, the removal rates of NH, were 71.3%, 84.0% and 93.2%; TP were 5.2%, 64.6% and 78.0%; TN were 46.2%, 50.3% and 75.5% separately in the three groups and the effect of group E was the best. CODcr, NH, and TP were decreased significantly compared with the contrast group A (p<0.05). Bivari-ate correlate analyze was done between the content of all size-fractionated chlorophyll-a, the percentages of all size frac-tionated contents to bulk contents with all environmental factors. The result showed that the percentages of Net-Chla% significantly negatively correlated with CODcr,TN, NH, and TP and positively with NO2-N and NO3-N, while the percentage of Nano-Chla% and Pico-Chla% positively correlated with CODcr, TN, NH, and TP and negatively with NO2-N and NO3-N. As both of the TN and NH4, TP and COD are indexes reflecting the level of the water contamination, results of the above analysis signified that the percentage of Nano-and Net-chla were closely correlated with the level of water contamination.