Abstract: [Objective]To synthesize the codon optimized endoglucanase-encoding gene and cellobiohydrolase-encoding gene and to realize their constitutive and secretive expression in Lactococcus lactis（L. lactis）. [Methods]The codons of endoglucanase-encoding gene of Piromyces rhizinflatus（P. rhizinflatus） cbh YW23-1（Gen Bank Accession Number：EU314937.1） and cellobiohydrolase-encoding gene of Fibrobacter succinogenes（F. succinogenes） end-1（Gen Bank Accession Number： X88561.1） were optimized according to the codons usage bias of L. lactis MG1363; the restriction enzyme sites of ClaⅠ/XbaⅠand Hind Ⅲ were introduced to the upstream and downstream of the two genes respectively to obtain the cloning vectors of p UC57-cbh YW23-1 and p UC57-end-1; after digestion by restriction enzyme,the two cloning vectors were connected with a constructed constitutive secretion vector p MG36e＋P32 ＋SPusp45,respectively; the obtained expression vectors for the two genes were introduced into L. lactis MG1363 by electrotransformation; the recombinants with high copy number were screened by erythromycin resistance selection; the CMC-Na was used as substrate to assess the activity and expression profile of the expressed endoglucanase and cellobiohydrolase. [Results]The secretive expression vectors for cbh YW23-1 gene and end-1 gene were successfully constructed; the two genes were highly efficiently and stablely expressed in L. lactis MG1363; the activity of endoglucanase and cellobiohydrolase expressed by the recombinant strains was 118.80 U/mL and 294.32 U/mL. [Conclusion]Two codon-optimized cellulose enzyme genes were successfully expressed in L. lactis,and the construction of the highly efficient genetic engineering bacteria lays the technical foundation for industrialized production of the two cellulose enzymes in the future.