Abstract: In order to analyze the anti-hepatic injury effect of enzymatic hydrolysate from Pinctada martensii (EP), we seperated EP by membrane ultrafiltration into three molecular size fractions MW> 10 kD (EP-Ⅰ), MW＝3–10 kD (EP-Ⅱ) and MW < 3 kD (EP-Ⅲ), and then measured the effects of three ultrafiltration fractions on the anti-ALD in vitro and liver-protection on mice. The results of experiments in vitro show that EP-III could activate alcohol dehydrogenase (ADH) significantly (P<0.01), and="" three="" fractions="" demonstrated="" different="" antioxidant="" capacities="">EP-Ⅱ>EP-Ⅰ). The results of mice experiment show that compared with the alcohol model group, the activities of ALT and AST in serum, liver index, the levels of MDA and TG in liver decreased in each ultrafiltration fraction group significantly, while the activities of SOD, ADH and ALDH and the levels of GSH in liver increased significantly. Therefore, the ultrafiltration fractions of enzymatic hydrolysate from soft tissue of P. martensii showed good protective effect on alcoholic liver damage, and the effect of EP-Ⅲ with low molecular mass was the best. Its mechanism may be related to accelerating ethanol metabolism and slowing down the oxidative damage caused by ethanol.