This study was performed to identify and analyze the specifically expressed plasma proteins during early pregnancy in both pregnant and non-pregnant Hanwoo. Blood samples were collected at 0 (the day of AI), 2, 3, 4, 7, and 11 weeks after AI from pregnant (n=3) and non-pregnant (n=4) Hanwoo, respectively. The hematological parameters were measured. After 2-dimensional electrophoresis using serum, normalized protein spots were selected for the significant expression variation deviated over two fold in its expression level between two groups. Among 17 spots selected, 15 were identified as albumin, IgG1 heavy chain constant region, haptoglobin, ferrochelatase, fibrinogen, hemopexin. 5 spots were expressed only in non-pregnant specific. The spot identification of 1105 and 6106 was decreased after 3 weeks from AI. However, 2/17 spots were still unidentified. Further studies are needed to analyze the function of the proteins associated with early pregnancy.