The secretion ability of the signal peptide of carboxymethyl cellulase (CMCase) was combined with the high expression ability of the Lactobacillus casei lactate dehydrogenase gene (ldh) promoter sequence (P-ldh) in Bacillus subtilis RM125. The CMCase was successfully secreted to the culture medium and the enzyme activity by P-ldh (11.2 U/ml) was approximately 4 fold higher than by its own promoter (2.7 U/ml).