Catalytic properties of halophilic exoglucanase from a marine Aspergillus niger and the secondary structure change caused by high salinity was analyzed under high salinities condition. Exoglucanase activity in 12% NaCl solution (w/v) was 1.32 folds higher of that in NaCl free solution. Half-life time in 12% NaCl solution (w/v) was over 1.41 folds higher of that in NaCl free solution. The exoglucanase had not endoglucanase activity. Gibbs free energy change of exoglucanase denaturation, Delta G, in 12% NaCl solution (w/v) was about 1.0 kJ/mol more than that in NaCl free solution at 45 degrees C, 50 degrees C, 55 degrees C and 60 degrees C. Melt temperature in 12% NaCl solution (w/v), 48.02 degrees C, was 3.32 degrees C higher than that in NaCl free solution, 44.70 degrees C. High salinity made contents of beta-sheet and alpha-helix increased. The secondary structure change caused by high salinities improved exoglucanase thermostability and activity. The halostable exoglucanase from a marine Aspergillus niger was valuable for cellulose hydrolysis at high salinities. (C) 2017 Elsevier Ltd. All rights reserved.