Abstract: The phenolic compounds of buckwheat,barley,rice and wheat were extracted with 70%(v/v)ethanol solutions and purified by AB-8 macroporous resin. Total polyphenol and flavonoid contents of the grain were quantified. And HPLC-MS was used to investigate phenolic composition of grains.The antioxidant properties of grain were investigated,and the anti-proliferative activity of grain extracts was analyzed by human colon adenocarcinoma Caco-2 cells. Correlation between polyphenol content and activity were also analyzed. The results showed that buckwheat had the highest contents of total phenolics and total flavonoids,followed by barley,rice and wheat. Among the four grains,21 major phenolic compounds were successfully identified in the grain extracts. The phenolic compounds of four grains had a certain antioxidant and anti proliferation ability of Caco-2 cells,with the order:Buckwheat,barley,rice,and wheat. Experimental results showed that total phenolic compound content had correlations with antioxidant activity and inhibiory effect to Caco-2 cells' proliferation.