Abstract: Cathepsin D is a major, lysosomal aspartic proteinase, which has important function in proteins degradation. In this study through in silico cloning and RACE, the full-length cDNA of cathepsin D was isolated and sequenced. Sequence analysis revealed a 2032 bp cDNA containing a 93 bp 5’-untranslated region, a 706 bp 3’-untranslated region and a 1233 bp open reading frame coding 410 amino acid ( Genbank accession number：DQ018727). By means of bioinformatics and internet resources , The deduced 410 amino acids of cathepsin D was predicted to contain an Asn （Asparagine）domain, a number of transmembrane regions, a signal peptide with 20 amino acid. And 3D structure of pig cathepsin D was similar to mammalian cathepsin D（alignment score is 99.7%）. Northern hybridization result revealed this gene has only one transcript and expression analysis indicated that cathepsin D was expressed widely and there was no difference within the four pig breeds，and no difference among the tissues.