Abstract: The effect of alfalfa (Medicago sativa) hay substituting for part of the concentrate on production performance, milk quality of dairy cows and economic profit was studied. Twenty-four multiparous Holstein lactation cows in mid lactation with similar body weights and milk production were selected and randomly divided into four groups. The diet for the control group included corn silage, peanut vine and concentrate, and in the test groups A, B and C, 3 kg alfalfa hay were used to substitute for 1.5, 2.0 and 3.0 kg concentrate, respectively, in 70 days of a feeding trial. The milk yield of the test groups was significantly (P<0.01) higher than that of the control group and milk yield of group A was significantly (P<0.05) higher than those of groups B and C, while there was no significant difference in milk yield between groups B and C. There were significant (P<0.05) differences between test groups and the control group in milk protein with groups B and C significantly (P<0.05) higher than group A. Compared with those of the control group, fat percentage (P<0.01), lactose and dry matter (P<0.05) of the test groups were significantly increased, but the differences were not significant between the three test groups. Dry matter intake of group A was the highest, and that of groups A and B were significantly (P<0.01) higher than group C and the control group, although, the difference was not significant between group C and the control group. Compared with that of the control group, somatic cell count of the test groups was reduced, but the differences between the four groups were not significant. The apparent digestibility of crude protein (P<0.05) and neutral detergent fiber (P<0.01) of groups B and C were significantly higher than those of the control group, but the difference was not significant between group A and the control group. At 7.92 yuan/days, the profit of group A was the greatest. This research has shown that substituting 3 kg alfalfa hay in concentrate can improve the milk yield, the quality of milk and the profit. Three kg alfalfa hay substituting for 1.5 kg concentrate is recommended.