The invention provides a release method for reducing the nicotine content of tobacco leaves by using a plant growth regulator. In the method, the plant growth regulator is dissolved in a release medium and is filled into conic caps to prepare release caps; and the release caps are covered at sections of the top of stems of tobacco plants. The method has the characteristics of novel concept, science, practicability, simple operation, easy mastery, relatively low cost and the like. The method is favorable for reducing the labor amount in using the plant growth regulators of the tobacco leaves and improving the utilization ratio and has significant effect of reducing the nicotine content of the tobacco leaves. The method provides a new idea and method for regulating the growth and metabolism of the tobacco plants in China tobacco industry, and can be widely used in areas producing the tobaccos.