In this study, the potted method was used. We sprayed triadimefon (TD) with different concentrations (100, 150, 200, 250, 300 mg·kg^-1) on the leaves of Zinnia elegans at the seedling stage, and then treated with natural drought and rehydration. The changes of agronomic and physiological characteristics of Z. elegans were analyzed, and the TD concentration with the best drought resistance effect was also selected to clarify the effect mechanism of TD on the growth of Z. elegans seedlings under drought stress, so as to provide a theoretical basis for the application of drought resistance cultivation and the breeding of resistant varieties. The results showed that: (1) different concentrations of TD pretreatment can significantly improve the drought resistance of Z. elegans seedlings, such as increasing the root length, stem diameter and root shoot ratio of seedlings, reducing the plant height and leaf area, so as to alleviate the damage caused by drought; it can also promote the increase of chlorophyll (Chl), soluble protein (SP) and proline (Pro) contents, improve the activities of peroxidase (POD) and superoxide dismutase (SOD) as well as slow down the increase of relative conductivity (REC) and malondialdehyde (MDA) contents. (2) After rehydration, the plant height, root length and stem diameter of each treatment increased, the contents of Chl, SP and Pro, and activities of POD and SOD increased, while REC and MDA contents decreased gradually. (3) Subordinate function analysis showed that TD with a concentration of 250 mg·kg^-1 had the best drought resistance effect on Z. elegans seedling.