Abstract: Nutritional evaluation of mixed ratio and effective microorganism （EM） on mixed silage made of alfalfa （Medicago sativa L.） and naked oats （Avena nuda） in different proportions （1∶0.5， 1∶1 and 1∶2） were carried out in present study. The changes between fermentation quality and nutrition composition were observed after 60 days. The results showed that the fermentation quality of silage was improved gradually with the increase of the proportion of naked oats. The pH value and the ratio of NH3\|N/TN were decline， and the lactic acid （LA） content was increased with the addition of EM. The contents of total volatile fatty acids （TVFAs） of the treatments with the addition of 0.1% EM and 0.2% EM were significantly lower than those of the control group （P<0.05）. The most significant effects on reducing the content of TVFAs and increasing the proportion of lactic acid and acetic acid were observed when alfalfa and naked oats were mixed in 1∶2 and with the addition of 0.1% EM. The content of crude protein （CP） was increased， and the content of neutral detergent fiber （NDF） and acid detergent fiber （ADF） were reduced with the increase of alfalfa proportion in mixed silage. The effects of EM on nutritional ingredient of mixed silage were not significant， and with the addition of 0.1% EM or 0.2% EM in mixed silage which the proportion of naked oats were increased， the consumption of water soluble carbohydrate （WSC） was accelerated， and the fermentation quality of mixed silage was improved. In a word， the mixed silage of alfalfa and naked oats could make nutrition complementary， improve nutrition value， and addition with 0.1% EM or 0.2% EM in mixed silage could help to depress bad fermentation and improve the fermentation quality.

Key words: alfalfa （Medicago sativa L.）, naked oats （Avena nuda）, silage, effective microorganism （EM）