Abstract: Chitosan was used as a flocculant to concentrate the active components from fermentation broth of Bacillus thuringiensis(Bt)LSZ9408.Chitosan dosage, rotation speed and rotation time of magnetic force stirrer,pH,and temperature for flocculation in the system were optimized.Results showed that a higher flocculation efficiency could be resulted in at pH 5.0-6.0,30-35℃, chitosan at 0.025%, and 5 min for stir at 550 r/min.Under the optimal conditions,most of water and tinct impurities were eliminated,and so the Bt insecticidal protein and spore was effectively concentrated.