Abstract: Pseudomonas sp. GX\-4-1 can produce flocculating substance PSD-1 in fish meal wastewater.This PSD-1 bioflocculant showed stable activity during a storage period of 325 days under low\|temperature storage.It had good stability under different pH values,with flocculating rate reaching over 90% for kaolin clay suspension.At pH of 12,this flocculant retained more than 50% of initial flocculating activity after 30 min of boiling in water.The bioflocculant roughly extracted through organic solvent precipitation and freeze\|drying exhibited high revived flocculating rate up to 99.66%.PSD-1 also has an effective act on solid suspension and E.coli suspension,with CaCl_-2 as flocculating assistant and under the alkali condition.