Abstract: [Objective]To evaluate the effect of microbial fermented-wet feed on milk yield and nutrient digestibility of Holstein cows.[Method]Cows were divided into four groups according to their milking capacity. Group 1 and group 2 were composed of high-producing cows, whereas group 3 and group 4 were composed of moderate- and low- producing cows. The group 2 and group 4 were set as experimental groups whose basal diet were supplemented with 2 kg fermented-wet feed per day. The group 1 and group 3, serving as control groups, were fed with basal diet without addition of fermented-wet feed.[Result] Significant effect of fermented-wet feed on milk yield of Holstein cows was observed (P<0.05);group 2 had higher feed intake compared to group 1;manure screener data showed that the percent of top screen of the experimental groups was generally reduced by 2.80% to 4.89% compared to group 1.[Conclusion] Dietary supplementation of fermented-wet feed in lactating period can significantly improve the milk yield and nutrient digestibility of Holstein cows.