Mung bean is mostly planted in flat terrain in Northeastern China. It is necessary to adjust the height of mung bean to make it resistant to lodging for mechanized harvest. We have known that S₃₃₀₇ could shorten plant height according to previous studies on many other crops. In this experiment, Bailv 9 was used as the test material to spray clear water（CK） and S₃₃₀₇ with concentrations of 90 mg/L, 120 mg/L and 150 mg/L at seedling stage, branching stage, squaring stage and flowering period. And measured internode length, plant height, height of podding, number of leaves, chlorophyll content and number of pods per plant to find the best period and concentration of spraying S₃₃₀₇ to shorten the height of mung bean. The two-year results showed that the effective of spraying S₃₃₀₇ at 120 mg/L in branching stage on the leaves of mung bean worked better, promoting leaves, chlorophyll content and pods per plant.