Abstract: To questioning the higher planting density leading to lower seedling rate and the difficulty of seedling maintenance of Medicago sativa in Hexi region of Gansu, the study investigates optimum planting density of M. sativa in Hexi region of Gansu. The results showed that grass yield depended on planting density of M. sativa. The optimum density was 6 millions grains per hectare. The density gave the highest grass and protein yields, of which were 24 776.66 and 4 924.5 kg/ha, respectively. However, with the planting density increasing, M. sativa showed advancing reviving in the spring, postponing florescence, decreasing plant height and dry matter, lower droughtresistance.