The standing herbage yield and quality affect the carrying capacity of grassland, the nutritional status and performance of herbivores. In this study, we chose the natural grasslands in Sanjiangyuan region and its surrounding areas, analyzed the temporal and spatial patterns of grassland primary productivity and herbage quality throughout one growing season (i.e. start, peak and end of the growing season). The results showed that aboveground herbage biomass, edible herbage and crude protein (CP) yields had apparent regional differences. Values of above three indexes were higher in the east and south parts than those in the middle and west parts of the Sanjiangyuan region. In most research areas, the gross primary productivity and edible herbage yields were the highest at the peak of growing season, and the lowest in the start of growing season. CP yield was the highest in the peak of growing season, and did not differ between the start and the end of growing season. While CP yield was the highest in the start of growing season, and was the lowest in the end of growing season in Kekexili district. In the whole Sanjiangyuan region, both CP content and CP yield were higher in the south part than those in the north part, and showed higher in the eastern agro-pastoral area than that in the western depopulated zone. Herbage CP content was the highest in the start of growing season, and the lowest in the end of growing season in all studied areas, while the seasonal fluctuations of other nutrient contents in different regions were not consistent. CP content of edible grass increased first and then decreased with the elevation increment. Crude ash content increased significantly, while neutral detergent fiber, acid detergent fiber and neutral detergent lignin decreased with elevation increment. In summary, standing herbage productivity, edible herbage yield and CP yield were higher in Sanjiangyuan region and its surrounding areas, and this kind of grass had better edibility. The herbage quality was relatively better in most areas of the Sanjiangyuan region, and the nutritional value of herbage was the highest (high protein, low fiber) in the end of growing season. The herbage yield and nutrient output peaked in the start of growing season. The nutrition quality of grass were poor during withering period, supplementary feeding should be carried out during this period to promote livestock performance. The available grassland was mainly distributed in the east, south and southeast parts of Sanjiangyuan region. The herbage quality and utilization potential (crude protein yield) are high in this region, where can be moderately utilized.