Abstract: This work is aimed to isolate the strains producing proteases from Daya Bay mangrove and to characterize the enzymatic properties and the optimal fermentation conditions. The clear zone method was used to screen strains，the Folin-phenol reagent method to determine the activity of protease，and the single factor experiments and the orthogonal experiments to determine the optimal fermentation medium and the fermentation conditions. Protease-producing Bacillus subtilis DH-2 was isolated from soil samples，and the optimal fermentation pH and temperature of the protease secreted by DH-2 were 8.0 and 65℃，respectively. The protease remained over 80% of its original activity after treatment for 60 min at 50℃. The protease tolerated multiple metal ions，organic solvents and surfactants. The optimal fermentation conditions for the protease were：1%（m/V）soluble starch，1% tryptone，1% NaCl，the initial pH of 5.5，and the inoculation amount of 7%，36 h culture at 40℃. Under optimal fermentation conditions，the enzyme activity of the fermented liquid was 236.30 U/mL，which was about eight times of the activity in initial screening. Conclusively，the protease has a relatively wide range of action temperature and pH，and exhibits fine resistance to multiple metal ions，organic solvents and surfactants，and is characterized stably.

Key words: marine microorganisms, protease, study of enzymatic properties, optimization of fermentation conditions