A genomic library of Cellulomonas sp. ATCC 21399 DNA was constructed in E. coli using plasmid pUC19. X-Glu and PNPG were to screen a genomic clone expressing j3-glucosidase, partially digested Pstl fragment of chromosomal DNA was inserted into the Pstl site of pUC19. The plasmid isolated from several clones which were sensitive to X-Glu and PNPG. The reconstructed plasmid, named pUJH 101, was isolated from E. coli transformations that produced β-glucosidase. Transformants, E. coli JM 109 harboring pUJH 101, was increased abour 1.6 times enzyme activity than that of Cellulomonas sp. The enzyme activity of transformant was increased 3 times by inducer, IPTG. The enzymatic properties, including optimal pH and temperature were invested, those were pH 7.5 and 50℃.