Abstract: A lactobacillus HJ-S2 with high effectiveness of cholesterol lowering was isolated from a beaked whale (Mesoplodon rostris) viscera using o-benzaldehyde method. The bacterium was identified as lactobacillus plantarum by 16S rDNA and API 50CH. In order to improve the cholesterol-lowering ability of HJ-S2 in vitro, the growth characteristics of the strain was investigated. Single factor and orthogonal experiment was used to optimize the condition in two aspects, the fermentation and medium. The optimized fermentation condition was set as follows: peptone 5 g/L, glucose 25 g/L, cholesterol 1.0 g/L, bile salt 2.0 g/L, temperature 37 ℃, pH 6, incubation time 24 h and inoculation amount 1%. Under the optimized condition, the cholesterollowering rate reached 69.81%, which significantly improved the result. Thus the optimized fermentation condition could offer production process and reference for further development in application of functional probiotics.