Abstract: Screening of DNA sequence similar with exo-1, 4-β-D-glucanase from the genome data of Bacillus licheniformis with bioinformatic techniques, one DNA fragment CelB showed high similarity was found. This DNA was cloned, expressed, and the result protein was purified. The CelB showed activity to cellulose substrate. Based on the conserved activity sites of glycoside hydrolase family 48 protein, amino acid sites of CelB were choosed for mutation and the mutant of CelB lost the activity, thus it showed that CelB contain the typical active sites of family 48. In this work, a exo-1, 4-β-D-glucanase gene was successfully found and cloned from B. licheniformis, it establishes the foundation for the further study of the cellulase system and their working mechanism of B. licheniformis.