In order to investigate the effects of LaCl3 on the growth and physiological characteristics of rice seedlings under drought stress, 15% PEG6000 was used to simulate drought stress. The effects of different concentrations of LaCl3 on the biomass, seedling index, root morphology, antioxidant system and malondialdehyde content of rice seedlings under drought stress were studied. The results showed that after spraying exogenous LaCl3, the indexes of rice seedlings under drought stress showed a concentration effect of low promoting and high suppression. 1 μmol/L LaCl3 can significantly promote the fresh weight of plants and the dry weight of aerial parts. 100 μmol/L LaCl3 can significantly increase the underground dry weight and seedling index, SOD activity of leaves and roots, CAT activity of leaves, and decrease of MDA content in roots. This study laid the foundation for the study of LaCl3 regulation of drought tolerance in rice seedlings.