In order to reveal the evolution of karst region after the returning farmland to forest project, six types of restored plantations including Castanea mollissima, Eucalyptus robusta Smith, Pinus massoniana Lamb, Zenia insignis Chun, Amygdalus persica Linn, and Illicium verum in Pingguo County of Guangxi Zhuang Autonomous Region were studied, and a seven-year grassland under enclosure was taken as control. The biomass allocations of different plantations were compared and biomasses were scored. Results showed that: 1) Total biomass per unit area ordered from high to low as C. mollissima > E. robusta > I. verum > P. massoniana > A. persica > Z. insignis. 2) For each type of restored plantation, the biomass of aboveground part is larger than that of the underground part. 3) The biomass of the herb layer is larger than that of the shrub layer in most of plantation types, but lower than the biomass of the seven-year grassland; 4) The dry litter weight per unit area ranked from large to small as C. mollissima > E. robusta > A. persica > Z. insignis > I. verum > P. massoniana; 5) Biomass composite scores ordered from high to low as I. verum > C. mollissima > E. robusta > P. massoniana >A. persica > Z. insignis. This project of returning farmland to forest can maintain ecological safety and promote the harmony between human and the nature, and still requires a long-term construction. Analysis of the ecological benefits of returning farmland to forest project has great significance to the nature and human.