Compared with other systems, the biggest advantage of mammalian cell expression system is the ability to the correct guidance of protein folding, provide complex type N glycosylation and accurate O glycosylation, and other processing after the translation function. In some cases, the activity of its expression product is far better than the prokaryotic expression system and eukaryotic expression system such as yeast, insect cells. Conventional experiments using most of the host cell is HEK 293 cells and CHO cells, the former is generally used for transient expression of recombinant proteins, used to in a short period of time for a small amount of bioactive recombinant protein; While the latter is commonly used in the stability of recombinant protein expression, CHO cells due to its stable genetic traits, growth faster, that can tolerate a certain amount of shear force and osmotic pressure and has similar to those of humans and the advantages of glycosylation modification, in industrial production and health play an important role. Our company provides instantaneous cells protein expression and stable cell strains build services, the company has strong industrial CHO GS expression system (namely "glutamine synthetase screening system"), through the screening system to build stable cell lines expressing CHO antibody water up to 3 g/L.