Effects of photosynthetic bacteria(PSB) on the aquiculture water quality such as chemical oxygen consumption(COD),ammonia nitrogen(NH₄⁺-N),dissolved oxygen(DO) and pH were investigated.Besides,the effects of PSB on the composition of population of hydrobios including phycophyta and water bacteria were also estimated in our studies.The results showed that PSB could reduce the organic content and NH₄⁺-N,but raise the DO content.At the same time,the phycophyta biomass could be affected by the PSB.In 0.50% group and 1% group,the phycophyta biomass was increased obviously.The proportion of the bacillariophuta was occupied up to 26%;the proportion of the chlorophyta was amounted to 60%;whereas the proportion of the cyanophyta decreased by 10%.Moreover,the composition of water bacteria population in the aquaculture water was effected by the PSB,with the proportion of vibrio and aeromonas decreasing obviously.