Cellulolytic bacteria are one of the bacteria that can produce cellulase enzymes which have an important role in degrading cellulose. Research has been carried out on testing the activity of cellulase enzymes from cellulolytic bacteria isolated in the waters of the mangrove ecosystem. The purpose of this study was to qualitatively examine the activity of cellulase enzymes from cellulolytic bacteria in the presence of a clear zone on Carboxy Methyl Cellulose (CMC) media while quantitatively the presence of enzyme activity and specific activity. Determination of the location of the sampling station is done by purposive sampling method. The sample is a sample sourced from the waters of the mangrove area taken from 4 stations, namely station 1 and station 2 located in Gampong Lam Badeuk and Gampong Deah Tengoh while stations 3 and 4 are located in Gampong Desa Ruyung and Gampong Desa Lamreh. The results of the enzymatic activity test qualitatively showed that from 17 bacterial isolates, cellulolytic indexes were obtained which varied and ranged from 0.46 cm to 2.71 cm. From all isolates, obtained 2 isolates that have the highest cellulolytic index, namely isolate BAM-112 (2.71 cm) and isolate BAM-326 (2.28 cm). The results of the quantitative enzyme activity test for the highest BAM-112 isolate was obtained at the 30th hour (0.008 U/ml) and the highest BAM-326 isolate was obtained at the 48th hour (0.0012 U/ml). Meanwhile, the specific activity test on isolate BAM-112 was highest at the 30th hour (0.251 U/mg) and the highest protein content was obtained at the 36th hour (0.057 mg/ml). The highest specific activity value in BAM-326 isolate was obtained at the 48th hour (0.097 U/mg) and the highest protein content was obtained at the 18th hour (0.014 mg/ml).