The cellabiase (${eta}$-glucosidase) gene in a Cellulomonas sp. CS1-1 was cloned into E. coli HB101 using the vector plasmid pBR322, and the expression of the gene in E. coli studied. The chromosomal DNA of the cellulomonas was digested by seveal restriction enzymes, each of which has only one cleaving site in plasmid pBR322. The recombinant plasmid, pSB2, created with Sal I frament, was expressed for the cellobiase gene in E. coli. The recombiant plasmid was estimated to contain 6.4 Kb foreign DNA at the Sal I site of plasmid pBR322 and the inserted DNA was mapped by single and double digestion with several enzymes. E. coli HB101(pSB2) has slowly grown in a mineral liquid medium containing cellobiose as a sole carbon source. The cellobiase activity in the transformed E. coli was 132 units per liter, which is equivalent to one twenty fifth of that in doner strain Cellulomonas sp. CS1-1. The transforned cell with plasmid containing cellulase gene grow well in the LB mediuns. The synthesis of cellobiase in the strain, E. coli HB101 (pSB2), was inhibited by glucose and at high concentration of cellobiose, and induced by cellobiose at low concentration.