In this study, the eggplant(Solanum melongena L.) seedlings planted in the nutritive soil cup were placed in high temperature condition for 24 hours after the leaves were sprayed by four different concentrations of melatonin solution( by water as control), then the indexes of the photosynthetic parameters, the activities of SOD, POD and CAT and the content of MDA were measured to study the effect of exogenous melatonin (MT) on photosynthesis and antioxidant properties of eggplant seedlings under high temperature stress. The results showed that foliar application of MT could effectively increase photosynthetic capacity and antioxidant properties of eggplant seedlings under high temperature stress. Compared with the other MT concentration treatments and the control, 150 μmol/L had the greatest effect on the contents of chlorophyll (3.69 mg/g) and net photosynthetic rate (12.14 μmol/m2?s), the activities of SOD(256.31 U/g) and CAT(41.80 U/g), the content of MDA(16.71 nmol/g). The contents of chlorophyll and net photosynthetic rate of 150 μmol/L were significant higher than those of the control, and there were no significant difference on the activities of the SOD and CAT between the 50 μmol/L and the 200 μmol/L, while the content of MDA of MT treatments were significantly lower than those of the control.