Abstract: In order to improve the degradation rate of carotenoids,optimization of the fermentation medium for Enterobacter hormaechei A20 strain was carried out by response surface analysis.The optimal carbon source,nitrogen source and inorganic salts source for A20 were glucose,a mixed nitrogen source( yeast extract∶ peptone= 2∶ 1) and K₂HPO₄,respectively.Then three critical factors were selected as response factors,the Box-Behnken response surface analysis test of 3 factors and 3 levels was designed with the degradation rate of carotenoid as the response value.As a result,the optimum fermentation medium was composed of glucose 8 g / L,mixed nitrogen sources( yeast extract∶ peptone = 2 ∶ 1) 14 g / L and K₂HPO₄ 0.72 g / L.Under the situation,carotenoids degradation rate increased from 45.7% to 77.37%,which increased by 69.30% compared with the original medium.The observed responses are in close agreement with the predicted values of the mathematic models,and the Box-Behnken design is suitable for optimize the culture medium of the degradation of carotenoids.