Studying on the change regularity of CTSB activity of sheep oocytes during in vitro maturation (IVM), and the relativity with developmental capacity of oocytes, could provide a theoretical basis and technical measures to improve the efficiency of sheep embryo production in vitro. The amplified CDS sequence of CTSB from sheep, a total length of 1008 bp, coding 335 amino acids, had been submitted to Genbank (accession number: KC699918). Using a variety of bioinformatics software predicted that E-64 sheep CTSB protein had the typical structural characteristics of papain-like cysteine proteases, consisting of signal peptide, propeptide and mature peptide. It had three cysteine protease active sites: Cys108, His278 and Asn298, and also a CTSB protein specific characteristic “occluding loop”. It also had modification of phosphorylation and glycosylation after translation.