Abstract: The aim of this research was the study of carbon cycle in the sea and isolation of new industrial strains. Samples of sediment and water were collected from some parts of Persian Gulf. First, the samples were enriched in Marine Broth medium. Then screening of cellulolytic isolates by using a congo red test were made on carboxymethyl cellulose (CMC) agar plates. The bacterial cultures were incubated in a shaking incubator at 37°C for 5 days. FPase and CMCase activity of cellulolytic strains was assayed and their enzymatic activity was drawn as a graph. The assay for the enzymatic activity was based on the release of glucose that was detected using dinitrosalicylic acid (DNS). In this study, 70 isolates of bacteria were isolated from sediments and waters collected from Persian Gulf. It was found that 43 isolates showed positive results with clear zone around the cultures. Therefore, It was demonstrated isolates of S-G20, S-G19 and W-G15 displayed the highest enzyme activity of 0.091, 0.089 and 0.084 U mL-1 for CMCase and highest enzyme activity of 0.079, 0.074 and 0.072 U mL-1 for FPase respectively. The phylogenetic analysis of these strains using its 16S rDNA sequence data showed that strain S-G20 had highest homology (98%) with Streptomyces variabilis, S-G19 showed 97% similarity with Kocuria rosea and W-G15 showed 99% similarity with Stenotrophomonas maltophilia. Although cellulose-producing organisms are rarely found in the sea, cellulose-degrading bacteria are commonly found in the sea.