Abstract: Objective: Using statistical optimization method to improve the yield of chitosanase from marine bacterium Renibacterium sp. QD1. Methods: Firstly, significant influencing factors were identified by two- level Plackett-Burman design ( PBD) . Then the path of the steepest ascent was utilized to approach the optimal region of the significant factors. Optimal concentrations of the medium were confirmed by response surface methodology.Results: Three elements were identified as the significant factors, and the optimal concentration was 14.23 g / L for chitosan, 4.72 g / L for yeast and 6.42 for initial p H. Checking experiment results indicated that the maximum predicted value was in good agreement with mean of measured value.Conclusion: The yield of chitosanase under the optimal medium reaches 608.11 U / m L of fermentation supernatant, which was 52.03% higher than before the optimization.