Abstract: Litopenaeus vannamei, Scylla serrata and Trachinotus ovatus were polycultured in the ponds which were in Shanwei, Guangdong province, China. Samples of water and sediment were taken from those ponds every 14 days. Quantitative indices of bacteria including heterotrophic bacteria, Vibrio, Bacillus and fecal coliform were tested in laboratory; water temperature, salinity, pH value and dissolve oxygen (DO) were tested. The dynamic variation of bacteria and those water quality indices in marine polyculture pond were investigated during whole culture season. The results showed that bacteria quantity in culture water was more lower than that of bacteria in sediment; the quantities of heterotrophic bacteria, Vibrio and Bacillus in water were 6.4*10^3~3.00*10^5 CFU/mL,0.1*10^3~1.65*10^4 CFU/mL and 0.06*10^3~1.09*10^3 CFU/mL, respectively; that quantity of bacteria in sediment were 5.8*10^5~2.95*10^7 CFU/g, 0.8*10^4~ 2.75*10^5 CFU/g and 6.1*10^4~5.30*10^6 CFU/g, accordingly; quantity of heterotrophic bacteria in water was significantly positive correlated with that of sediment (P<0.05). The results of correlation analysis on water quality and bacteria quantity indicated that DO was an important index to aquaculture, the correlation between DO with quantity of Bacillus was positive significantly, but that correlation with Vibrio quantity was negative insignificantly.