Abstract: The optimum media composition and fermentation conditions were studied for chitin deacetylase( CDA)production by a screened marine filamentous fungus. Using single factor method and orthogonal experiment in test,the best culture conditions of enzyme was obtained as followings: cultured for 108 h at p H 6.0,and 30 ℃,,the media consist of glucose 7 g / L,yeast extract 7 g / L,Ca Cl20.75 g / L,chitin 1.25 g / L and Na Cl 1.4%.Moreover,after the determination of enzyme activity,it was found that the marine filamentous fungus mainly produced extracellular enzyme.Under this condition of the fermentation,the highest chitin deacetylase activity reached 21.37 U / m L. In general,it was a chitin deacetylase producing strain that had the potential to carry out research further.