Abstract: To understand the growth regularity and confirm the best harvest time of Forage grass oats, its plant height, fresh and dry matter accumulation and distribution during different stages in a field experiment were investigated, its nutrient values and relative value of feed were studied. The height of forage oat from booting stage to waxy stage was consistent with Logistic growth model ,under dry farming condtions. The changes of fresh dry ratio, stem/leaf ratio and hay yield were consistent with the linear regression model with the lowest booting stage and the highest waxy stage. Reached the highest grass yield of the ratooning buds of 33777.78 ㎏/hm2.Hay yield increased continuously from booting stage, reached the highest waxy stage is 10184.71 ㎏/hm2. Crude protein content in dry matter was the highest at flowering stage, 10.00%, and the lowest at waxing stage, 7.07%. The relative value of feed (RFV) was the highest in the ratooning buds, which was 95.85, followed by waxy stage, which was 86.03. It is suggested that under the condition of dry farming in northern Shanxi, forage grass oats should be harvested from flowering stage to ratooning buds when preparing silage, hay should be harvested from ratooning buds to waxy stage.