Mechanized harvesting can improve the work efficiency of large-scale planting of mung beans, so it is urgent to solve the problems such as inconsistent maturity period and incomplete leaf shedding during harvest in production. Ethephon can be used to promote crop maturity, increase yield and accelerate abscission layer formation leading to organ dropped. In this experiment, Bailyu No.9 was sprayed with clear water（CK） and ethephon at 0.20%,0.35% and 0.50% in 15 d, 12 d, 9 d and 6 d before harvest respectively in 2017 and 2018. The yield and main characters were measured to screen for the best period and concentration. The results of two years experiments showed that the effect of spraying ethephon in 15 d before harvest was better than other periods, the effect of spraying ethephon at 0.20% was better than other concentration; the leaves of different treatments were all less than CK, the chlorophyll content of different treatments were all less than CK. There was no significant difference in plant height between CK and different treatments, the effect of spraying ethephon at 0.20% in 15 d before harvest was smallest in pods per plant. Based on the two-year experimental results and considered the cost, it was useful for mung bean to promote the defoliation and increase the yield of mung bean by spraying ethephon on leaves, and the best spraying period for mung bean was 15 d before harvest, the best concentration of ethephon was 0.20%.