The invention discloses an immortalized dairy cow mammary epithelial 
cell line, a construction method, and applications thereof. In the provided construction method, Chinese Holstein cow epithelial cells are taken as the host cells, 
retrovirus carriers with SV-40-large T 
antigen are used to infect host cells, and finally a strain of immortalized dairy cow mammary epithelial 
cell line that can perform stable passage is screened out. The microbial preservation number of the strain is CGMCC No.8707. The constructed immortalized dairy cow mammary epithelial 
cell line has a stable property, the 
cell morphology is similar to that of primary cells after 40 generations, and the cells grow faster than the primary cells, can characteristically express mammary epithelial 
cell specific proteins, and maintain the synthesis functions of 
milk fat and 
milk protein. The immortalized dairy cow mammary epithelial cell line can be used as a 
cell model which is widely used in the fields such as 
milk component synthesis, 
milk secretion mechanism, research on laticiferous cell 
apoptosis and 
mammary gland degradation mechanism, and the like, and can be used as a 
mammary gland bioreactor to produce bioactive proteins.