[Objective] To optimize the fermentation conditions of Streptomyces strain MY0504 from marine environment and improve the fibrinolytic activity in fermentation broth. [Methods] Based on the growth curve of MY0504 and single factor test, the main factors affecting enzyme activity were found through the Plackett-Burman design, and the fermentation conditions were further optimized using steepest ascent experiment and Box-Behnken central composite design. [Results] The optimal fermentation conditions were as f...