Abstract: The standing crop and chemical composition of seston were investigated in 1983 in Chenhu flooding area, Wuhan. During the surveying period from May through September, the average DW (dry weight), AFDW (ash-free dry weight), Ash, C(carbon) and N (nitrogen) of sestonic standing crop were 5.24, 2.55, 2.69, 0.830 and 0.193 mg/1 respectively, which were all lower than those reported in eutrophic lakes by some authors. The seasonal changes of sestonic standing crop were prominent. The highest concentrations of DW, AFDW, Ash and N were recorded in the start of filling, coincident with great input of allochthonous seston, but the highest concentration of C was recorded in the late high water level phase, coincident with the formation of detritus in great amounts during the decomposition of plant litter; the lowest concentrations were all recorded just before the end of filling because of great sedimentation rate of seston. It was estimated that the concentrations of AFDW, Ash, C and N of seston were equivalent to 51.60, 47.50, 18.30 and 3.90% of its DW; the concentrations of seston C and N were equivalent to 36.40% and 7.70% of its AFDW. The average AFDW/Ash and C/N were 1.24 and 4.74. These two parameters could be used to assess the nutritive quality of seston in aquatic ecosystems. The significant linear relationships between DW and AFDW, C, N; between AFDW and Ash, C, N; and between C and N were all established, which indicated that they changed in the same manner.