The yeast protein expression system is the most economical and efficient eukaryotic system for secretion and intracellular expression. A protein expressed by the mammalian cell system is of very high-quality and close to the natural protein. But the low expression level, the high cost of medium and the culture conditions restrict the promotion of mammalian cell expression systems. The yeast protein expression system serve as a eukaryotic system integrate the advantages of the mammalian cell expression system. A protein expressed by yeast system could be modificated such as glycosylation, acylation, phosphorylation and so on to ensure the native protein conformation. It can be used to produce protein material with high added value that is very close to the natural protein. Our proteins produced by yeast expression system has been used as raw materials for downstream preparation of monoclonal antibodies.