Abstract: In order to explore the optimal mixed application of organic fertilizer and chemical fertilizer for alfalfa planting, the experiment was carried out in Fulaerji District, Qiqihar City, the western part of Songnen Plain, and study on the combined application of chemical fertilizer and cow dung fermentation organic materials.The yield and nutritional quality（acid detergent fiber, neutral detergent fiber, crude fat, crude fiber, crude protein, crude ash, relative feeding value） of alfalfa and soil physical and chemical property indexes（organic matter, alkaline hydrolyzed nitrogen, available phosphorus, available potassium, pH value） after different fertilizer treatments 30% organic fertilizer + 70% chemical fertilizer（T1）, 50% organic fertilizer + 50% chemical fertilizer（T2）, 70% organic fertilizer + 30% chemical fertilizer（T3）, 100% chemical fertilizer（T4）, 100% organic fertilizer（T5） and no fertilizer（T6） were measured for experimental. The results showed that fertilization could significantly increase the yield of alfalfa compared with T6 treatment（P＜0.05）, and T3 treatment increased the yield by 7.98% compared with the T6 treatment. Fertilization significantly increased the content of crude protein and relative feeding value（P＜0.05）, and the acid washing fiber content in T3 treatment decreased by 4.64%, 9.16% and 14.20%, respectively, compared with T4,T5,T6 treatment, and the neutral washing fiber content decreased by 3.93%, 6.00% and 11.60%, respectively. The content of available phosphorus in T3 treatment was significantly higher than T1,T4,T5,T6 treatment（P＜0.05）, which were increased by 35.82%,62.73%, 52.90% and 117.54%, respectively. The results indicated that the reasonable combination of organic fertilizer and chemical fertilizer could increase the yield and quality of alfalfa and improve soil fertility conditions, and the combination of 70% organic fertilizer + 30% chemical fertilizer had the best effect in this experiment.