Abstract:Importance value-area curve is used as a criterion for Judging the minimal area of a community. It seems to be better and more significant than other ones.Importance value-area curve used as a sampling technique, is suitable for tropical rain forests and montane rain forests in Hainan, and subtropical evergreen-broadleaf forests and evergreen needle-leaf forests in Guangdong. It has been shown that importance value-area curve has higher precision and higher efficiency.This paper suggests the formulas:used for the importance value-area curve to determinine minimal area.