The invention discloses a soybean height control and lodging prevention method which comprises the following steps: applying a regulator from a true leaf unfolding period to a first compound leaf unfolding period of soybeans, wherein the active ingredient in the regulator is cyclopropylamic acid. By adopting the height control and lodging prevention method, for the soybeans cultivated under the weak-light plan ting condition in relay intercropping and intercropping modes, the plant height can be effectively controlled, the lodging rate can be reduced, the seedling strengthening effect can be achieved, and accordingly the yield can be guaranteed. In addition, the regulator in the height control and lodging prevention method is convenient to apply.