Cellulase is an enzyme used in many fields, such as agriculture, industry, and medicine. Among microorganisms capable of synthesizing cellulase, bacteria are evaluated as having high enzyme activity, stability, and limited environmental pollution. This study was conducted to isolate and characterize bacteria strains with high ability to degrade cellulose, which can serve as a basis for research treatment methods for cellulose-containing agricultural by-products more effective. From wood processing by-products collected in two provinces, Hung Yen and Hanoi, by inoculating method on a selective medium containing 1% CMC (Carboxymethyl cellulose), 23 strains of bacteria capable of degrading CMC (carboxymethyl cellulose) were isolated, two strains, C4 and C2,1 were potential strains showing high ability to degrade carboxymethyl cellulose. Colony morphology, cell morphology, and biochemical characteristics showed that both strains belonged to genusBacillussp. After evaluating effects of culture conditions on cellulase activity of two selected strains, strain C4 synthesized cellulase with the highest activity when cultured in LB medium, shaking condition, at 35C, pH 8.0 for 24 hours; while strain C4 synthesized cellulase with the highest activity when cultured in LB medium, shaking condition, at 35C, pH 6,0 for 72 hours. Finally, evaluation of the ability to decompose rice straw and rotten wood in vitroshowed that the efficiency of these strains increased 3.02-4.22 times compared with the control.