Abstract: In order to explore the effect of exogenous melatonin (MT) on the physiological characteristics of sweet sorghum under drought stress at germination stage, the sweet sorghum variety Hercules was used as material, and the effect of melatonin initiation treatment on seed germination of sweet sorghum under drought stress (10% PEG simulation) were studied. The results showed that 10 μmol/L and 25 μmol/L melatonin initiation treatments could significantly increase α-amylase activity during seed germination under drought stress, reduce root tip cell damage, significantly increase the contents of endogenous gibberellin and auxin, accumulate more proline, and promote the increase of seed germination potential, vitality index, root length and root surface area. The 100 μmol/Land 500 μmol/L melatonin induced sweet sorghum seeds, aggravated seedling root tip damage, sharply increased auxin content and inhibited root growth in arid environment. In conclusion,10 μmol/L and 25 μmol/ L melatonin had the best effect, which can promote the synthesis of endogenous gibberellin and auxin by increasing starch hydrolysis, maintain strong osmosis, and enhance the drought stress resistance of sweet sorghum at germination stage.