Abstract: Soil fertility and elucidative density are important factors affecting biological properties of field mint, such as total leaves of main stem, quantity of stem, total leaves of small stem, quantity of efficacious leaves among these properties, total leaves of small stem relieved more influence, and the degree of influence can be impressed by the ration of total leaves of small stem to main stem. So by means of measuring the ration of stem to leaves of different cultivate density, we can know soil fertility as an important basis for Appling fertilizer. If we combing Appling fertilizer experiment and merry years produce practice with above knowledge, we wan figure out the ration of stem to leaf, coefficient of Appling fertilizer and quantity of fertilizer needed, that is to say, we can obtain a completely system of applying fertilizer according to ration of stem to leaf.