Abstract: The seasonal variations in the N, P, K, Fe and ash contents of 9 range plants were studied by half-monthly samplings from the same site in the Stipa grandis steppe at the Inner Mongolia Grassland Ecosystem Research Station (GERS) from May to October, 1981.Trends in crude protein(CP)and P were similar in grass and nongrass plants. Highest concentrations occurred at the ends of May and June, and the lowest in October, The seasonal variations were related with the growth rhythm of plant. Because precipitation affects the growth rhythm of plant, so it influences the seasonal variations of nutritional composition. The ash variations are different for grass and woody plant. The variations of grass belong to the concentrated type and its concentration in the later stage is less than in the earlier one; but the variations of woody plant is too so marked, There is authentic regression interrelation between the crude protein Concentration and the phosphorus concentration. The P concentration of harvested grass is lower because its concentration in harvest period was low.