Abstract: 【Objective】 The study aimed at exploring the alleviation effect of exogenous melatonin（MT）on garden chrysanthemum under drought stress and screening its suitable concentration,providing reference for planting garden chrysanthemum in arid and semi-arid areas.【Method】 With the garden chrysanthemum Xuanqiu ninghong as the test material and the 20% PEG as a drought stress penetrant,the different concentrations of MT（50,100,150,200 μmol/L） were sprayed on the leaves to study the its effects on the growth and physiological indexes of chrysanthemum seedlings under drought stress.【Result】 Under the drought stress conditions,the exogenously spraying of 100 μmol/L MT could effectively alleviate the damage caused by drought stress to the garden chrysanthemum seedlings. Compared with the PEG treatment,the chlorophyll content and relative water content of the leaves increased by 37. 4% and 69. 1%,respectively,and the relative conductivity（REC） and malonaldehyde content（MDA） decreased by 55. 7% and 42. 8%,respectively. Hydrogen peroxide（H2O2） increased by 75. 0%,and proline（Pro） by 60. 6%. The activities of superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT） were 1. 9,2,and 3. 2 times of PEG treatment. The results of the Principal Component Analysis showed that exogenous MT mainly had a great influence on the chlorophyll content and relative water content of leaves,and on the fresh weight of shoots of garden chrysanthemum.【Conclusion】 This study showed that the exogenously spraying of 100 μmol/L MT could effectively alleviate the damage to the garden chrysanthemum Xuanqiu ninghong caused by drought stress,improving the drought tolerance of the cutting seedlings.