A bacteria strain DY3 with high endoglucanse activity was isolated from deep sea sediment sample ES0109. The 16S rDNA sequence of DY3 exhibits identity of 99% with those of the same genus bacteria Pseudoalteromonas citrea and Pseudoalteromonas elyakovii . The celX gene of DY3 obtained by PCR method is 1479bp in length and encodes a protein of 492 amino acids. The protein encoded by celX gene exhibits 95% sequence identity with endoglucanase CelG from Pseudoalteromonas haloplanktis. There are two modules in the deduced amino acids sequence, a catalytic domain of glycosyl hydrolases family 5 at the N terminal and a carbohydrate binding domain at the C terminal which was linked to catalytic domain by a short linker. The optimal temperature of CelX is 40 degrees C and the optimal pH was between 6 and 7.