Abstract: The rice Nipponbare (lowland rice) seedlings were used to study the effect of 0.1 μmoL/L coronatine (COR) on the biomass accumulation,activity of antioxidative enzymes (SOD,CAT and POD),osmotic adjustment substances (proline and soluble sugar),soluble protein and endogenous hormones (ABA,IAA,Me-JA,ZR and GA4) contents under 17.5% PEG simulated drought stress.The results showed that COR treatment had no obvious effects on the biomass accumulation,activity of antioxidative enzymes,osmotic adjustment substances and soluble protein contents,but it improved the contents of ZR and GA4 under normal condition.While under simulated drought stress,the COR treatment could enhance the biomass accumulation,maintain the activity of antioxidative enzymes at a higher level and promote the accumulation of proline,soluble sugar and soluble protein in order to regulate the plant osmotic potential and cell turgor.The contents of ABA and ZR were also significantly improved with COR treatment.On the whole,COR could enhance the drought stress tolerance of lowland rice through improving the activity of antioxidative enzymes,regulating the contents of osmotic adjustment substances and endogenous hormones.