Abstract: In order to explore the effects of drought stress on seedling growth and carbon and nitrogen metabolism of different drought-tolerant ornamental grasses, relatively drought-tolerant, intermediate and relatively drought-sensitive ornamental grasses were selected which are Elymus magellanicus, Spartina anglica 'Aureomarginata' and Miscanthus transmorrisonensis. Four different water treatments used to compare and analyze the differences in seedling growth, carbon and nitrogen metabolism key products and related enzyme activities in response to drought stress. The results showed that drought stress inhibited the growth of plant height and diameter of three kinds of ornamental grass, and inhibited the drought-sensitive ornamental grass to a greater extent, with the maximum inhibition rates of 51.7% and 34.3% respectively. In terms of carbon metabolism, drought-tolerant ornamental grass showed higher soluble sugar content and SS, SPS activity. Under moderate drought conditions, the growth rate of drought-tolerant ornamental grass was increased by 9.8, 12.5, 31.7 percentage points compared with sensitive ornamental grass, relative to control group. In terms of nitrogen metabolism, drought-tolerant ornamental grass had higher content of free amino acids and soluble proteins, the highest content was 54.2%, 23.7% higher than control, and 20.1, 11.7 percentage points higher than drought-sensitive ornamental grass when the content of was highest. In addition, GS activity showed an increasing trend in all three ornamental grasses, but the drought-sensitive ornamental grass showed a slower change, and the activity of GOGAT and NR was lower than drought-tolerant ornamental grass. Drought-tolerant ornamental grass enhances its ability to cope with drought stress through more stable carbon and nitrogen metabolism, and there were differences in the main response substances of carbon and nitrogen metabolism in the seedling growth of different drought-tolerant ornamental grasses to drought stress.