Abstract: Through the improvement of both the ways of preparation and the methods of application , better effects of the immobilized PSB on the purification of water quality were achieved . Four kinds of immobilized carrier were tested .The results showed that the calcium alginate gel pellets containing 3 % permutite was better than others in the aspects of both pellet strength and the activity of purifying water quality .The decrease of NH3 -N ,NO2 -N concentration and the value of COD in the water varied in step with the increase of the embedding-ratio .The proper dosage of the immobilized PSB and the methods of activating immobilized PSB were studied .The experiments in production scale was carried out in 50m 3 zoeae rearing ponds .The highest zoeae survival rate of 40 .6 %was found in the pond where 19kg of immobilized PSB were added .Compared to the pond where free PSB were added in the same dosage , the zoeae survival rate was increased by 11 .2 %.Thus , the harvest of megalopa increased by 157 .5 thousands pieces of larvae per pond .