Abstract: This paper discusses the application of an age implicit growth model to the National Continuous Forest Inventory (NCFI).The error of the model is related to the projection interval ΔA and will be zero when ΔA is zero. An example taken from that age-explicit Johnosn Schumacher model is used as a base model from which an age implicit form is derived. The experimental data are Masson pine′s from Zhejiang Province′s NCFI. The estimation precision of 5 years′ total increment is greater than 80% for 95% confidence. The derivation,properties and error estimation of the model are presented. Data to be used for building age-implicit models must be those of being remeasured and matched. It is easy to use the model. Age-implicit models could be built at province level by tree species or group without considering the differences of plantation and natural,even-aged and uneven aged,pure and mixed,dominant and nondominant,as well as stand trees and scattered trees.