Abstract: During 1990~1991, in the nursery of the Chinese Academy of Forestry, leaf-plucking experiment of one-year-old Populus deltoides was conducted. The changing law of photosynthesis rate, stomatal conductance, stomatal resistance, main stem height growth rate and enlarging rate of leal area were observed, which proved the existance of over-compansation effect and expounded the characteristics of over-compensation effect in different growth stages, different leaf-plucking amount and different duration after leaf plucking.