Pregnancy failure caused by early embryonic death in dairy cows can result in significant economic losses to the dairy farm.Early and accurate pregnancy diagnosis in non-pregnant cows will improve the efficiency of pregnancy and shorten the number of days to nulliparity.This pa-per reviews recent domestic and international studies on pregnancy-associated proteins,body fluid proteins such as blood,urine,and milk of cows in early pregnancy stages,and proteomics to identify potential proteins in early non-pregnancy for accurate pregnancy diagnosis in early preg-nancy and to improve dairy production efficiency.