Abstract: The effects of melatonin treatment on physiological characteristics and quality of passion fruits during post harharvest storage were valuated. The passion fruits were dipped in 0, 0.05, 0.10, 0.20 mmol/L melatonin (MT) solution for 1 hour, then put in crisper and stored at room temperature (25±1 ℃), the parameters of firmness, color, soluble solid, soluble sugar and other indexes were analyzed. The results showed that more than 77% of the passion fruits in the CK group had rotted on the 12th day of storage, the mass loss rate and decay rate of melatonin treatment group were 8.22%~12.81% and 22.22%~38.89%, which were significantly lower than those of CK group (P<0.05), the melatonin treatment groups kept a good quality and the contents of soluble solids, titratable acid and soluble sugar were significantly higher than CK group (P<0.05). On the 16th day, all the fruits in CK group had rotted, the firmness of passion fruits treated with 0.20 mmol/L melatonin was 9.95 kg/cm², which was significantly higher than that in the other two melatonin groups (P<0.05), and the weight loss rate was only 15.52%, which was significantly lower than that in the other two treatment groups (P<0.05), while other quality parameters had no significant differences between the other two treatment groups. In conclusion, 0.05, 0.10 and 0.20 mmol/L melatonin treatments could prolong the storage time of passion fruits and maintain the quality at a high level, while 0.20 mmol/L melatonin treatment had the best effect.