A new kind of high flocculants-producing bacteria JX18 was isolated from sludge samples. It was identified as a Pseudomonas fluorescens based on its morphological, physiological characteristics and the partial sequences of its 16S rRNA. The bacteria reached stationary phase after culturing 40 h, and had a maximum ?occulating activity after culturing 48 h. The further investigation indicated that the optimum flocculants-producing conditions obtained were initial pH 7.0, temperature 30oC, rotation speed 160 r/min, glucose and peptone were chosen as the optimum carbon and nitrogen sources. Optimum cultivation conditions, the flocculation efficiency toward a gaolin clay suspension reached 90.56%.