Abstract: The authors examined the response of G. pentaphyllum population behavior to soil fertility, using the semi-controlled experimental method. The results show that the increase of soil fertility can significantly increase the biomass allocation ratio of reproductive organs, and decrease that of non-reproductive organs, that the ratios of foliage and supporting parts decrease little with increasing soil fertility; that the increase of soil fertility does not significantly affect the morphological characters and mean relative growth rate of the populations; that most of the reproductive characters respond to the increase of soil fertility significantly. The conclusion is: different behaviors of the G. pentophyllum populations have different sensitivities to the change of soil fertility.