To investigute the effect of different roughage source on milk yield and composition in dairy cows, two experiments were conducted by using 9 Holstein cows. The cows were allocated to 3 x 3 Latin square model and fed bahiagrass hay, timothy hay and alfalfa hay. Corn silage and Italian ryegrass silage were fed in trial 1 and trial 2, respectively. The composition and in vivo digestibility of nutrients in diets were measured. The concentration and digestibility of crude protein and the concentration of calcium in alfalfa hay were quite higher than those in timothy and bahiagrass hay. The concentration and digestibility of crude fiber in alfalfa hay were lower than those in timothy and bahiagrass hay. The concentration and digestibility of crude protein in Italian ryegrass silage were lower than those in corn silage. In both of the trials, the dry matter intake and milk yield of cows fed bahiagrass hay tended to be lower than those of cows fed timothy and alfalfa hay. The concentrations of milk fat from cows fed alfalfa hay were the lowest in the treatment groups. Conversely, the concentrations of milk protein from cows fed alfalfa hay were the highest in the treatment groups. The rate of dry matter intake in cows of trial 2 were lower than that in cows of trial 1. The decrease of milk yield in trial 2 since the beginning of the experiment was larger than that in trial 1. The milk yield was given by the regression equation of the independent variables of dry matter intake and liveweight. The concentrations of milk fat and lactose were given by the regression equation of the independent variables including milk yield and liveweight. The results from this experiment suggest that milk yield and milk composition in dairy cows may be affected by the difference of roughage source.