Abstract: A microbial flocculant producing strain named WZ with good flocculation effect to ASP produced water was screened out from ASP produced water. We detected and accomplished the sequence analysis of 16S rDNA for strain WZ and studied flocculating effects when putting metabolite produced by WZ strain into ASP produced water, analyzed main active ingredients in WZ flocculant. The results illustrate that WZ strain belongs to Pantoea Agglomerans and the flocculant produced by WZ strain are mainly distributed in the supernatant of fermented liquid through centrifuged. The flocculating effect on ASP produced water is the best under the conditions that WZ strain is placed in a shaker to cultivate for 29 h at 35 ℃ and 170 r/min. The optimum addition volume of the microbial flocculant is 25 mL/L and the removal rate of suspended solids can reach 47.76%. By approaches of Anthrone colorimetric, Bradford method and infrared spectrum analysis, it is concluded that the main ingredient in the microbial flocculant is glycosidoprotein.