Abstract: The complexes between Fast Green FCF dye and the damaged part of a grain were vivid,and were soluble in sodium hydroxide solution. The study established a biochemical method for evaluation of grain damage by FCF dye. Five to twenty grams of samples were soaked for 20 min by 10 to 40 m L of 0.1% FCF dye dissolved in 0.01 mol·L~(-1)Na OH solution,then the samples were rinsed off by distilled water till no blue color in washed water,finally the samples were bleached in 10 to 40 m L of 0.01 mol·L~(-1)Na OH for 30 min in order to recover the complexes formed between FCF dye and the damaged part of grain. The bleaching solution was used to determine absorbency in 610 nm. This protocol was carried out within 1 hour for determination of grain damage. The damaged rates for shelled corn,brown rice,and wheat were respectively detected by this method over the range of 40%,60% and 20%,but it can't be used to detect the breakage percent of milled rice and soybean. The linear equations of between OD_(610)(y) and sample breakage percent(x) for shelled corn,wheat,and brown rice were y=0.034x+0.316,y=0.071x+0.204,y=0.049x+0.206 and,respectively,with determined coefficient higher than 0.998.