The species of forage crops used in this study were Italian ryegrass (cv. Kowenery), sorghum (cv. SX17), proso millet (cv. domestic) and Japanese millet (cv. Jeju). The plant height of the summer crops was the highest at the dough stage. The dry matter yield of Italian ryegrass was 902.7 kg per 10 a. The dry matter yield of the winter crop and sorghum was 11,985 kg when harvested at the dough stage rather than at the first and second harvests. The proso and Japanese millet also had higher yields for dry matter during the dough stage rather than during heading and regeneration. The acid detergent fiber (ADF) content of Sorghum was lower than that of the first and second harvest; however, the proso and Japanese millet had a higher ADF content at the dough stage. The neutral detergent fiber (NDF) content was higher at the dough stage than at the first and second harvest, and the crude protein content was also lower at the dough stage than at the first and second harvest. The crude protein production for the dry matter yield was about 84 kg in Sorghum when harvested at the dough stage. Proso millet showed no difference for the crude protein production at the heading and dough stage while the Japanese millet had a higher crude protein production. There were no differences in the total digestible nutrients (TDN) content for the three crops according to the harvesting time. Therefore, if Sorghum and Proso and Japanese millet are to be combined with Italian ryegrass, it is better to harvest them at the dough stage.