Abstract: Forage value and productivity are important grassland traits. Plant community ANPP, crude protein, crude fiber, crude ash, ether extract, calcium, phosphorus and nitrogen-free extract were measured and analyzed under different grazing systems during two hydrologically contrasting growing seasons in a desert steppe. The results showed that grazing significantly decreased community ANPP in 2011 which was dry. ANPP was the highest after 60 days without grazing in 2012, a wet year. In 2011 plant community ANPP, crude protein, crude fiber, crude ash, ether extract, calcium, phosphorus was 2.67, 1.08, 1.27, 1.26 and 3.75 times that in 2012. The highest crude protein and phosphorus content was detected after 60 days without grazing. With continuous grazing, crude protein, ether extract, crude ash, calcium and phosphorus content initially increased and then decreased; peak values occurred in July or August and the lowest values were found at the end of the growing season (October). However, crude fiber and nitrogen-free extract was lowest in July and highest in October. Precipitation has a major influence on community ANPP and the seasonal dynamic of community forage quality; grazing and yearly rainfall variation co-limited the change of community forage nutrient content.