Since the 1980s, the embryo engineering biotechnology, such as in vitro oocyte maturation (IVM), in vitro fertilization (IVF), embryo culture (IVC), embryo transfer (ET), nuclear transplantation has been developing rapidly . Young animals superovulation technology because it can fully exploit the reproductive capacity of dams, shorten the interval cycle times, accelerate the process of genetic improvement, also in vitro embryo production plays an important role. However, in vivo developmental capacity compared with oocytes and embryos in vitro oocyte maturation and fertilization rate was still relatively low, the difference between the developmental potential of embryonic formation, often after embryo transfer can not continue to lead the development and implantation failure. Especially lambs, calves and other young animals, their developmental potential of embryonic worse compared to adult animals. Therefore, how to improve young adult animals and animal oocyte maturation effects and the ability to follow the development of embryos, is still an important part of art embryo engineering E-64 research. Cathepsin B (cathepsin B, CTSB) is a lysosomal cysteine protease important, play a role in many physiological and pathological events, such as apoptosis, tumor invasion and metastasis, with its animal oocytes cell maturation and embryo development also has an important impact. CTSB in the process of understanding the regulation of oocyte development in its conduct of foreign intervention, can provide an effective means to improve the ability of an animal embryo development in vitro.