Kinetics of cellulose hydrolysis with halostable cellulase from a marine Aspergillus niger was analyzed at different salinities. Cellulase activity in 8% NaCl solution was 1.43 folds higher than that in NaCl free solution. Half saturation constant, K-m (15.6260 g/L) and the rate constant of deactivation, K-de (0.3369 g/L h) in 8% NaCI solution was lower than that (18.6364 g/L), 0.3754 (g/L h) in NaCI free solution. The maximum initial hydrolysis velocity, V-max (25.5295 g/L h), in 8% NaCl solution was higher than that in NaCl free solution (25.0153 g/L h). High salinity increased affinity to the cellulase to the substrate and thermostability. Halostable cellulase from a marine Aspergillus niger was valuable for cellulose hydrolysis under high salinity conditions.