In this paper, the author treated the forest growing system as a linear system and took the nursery stock growing system as an example. And a least square identification method was presented for a "multi-input-multi-output" linear static system in forestry. The method was further extended to the linear dynamic system and was used to solve the problems in the parameter identification of Picea asperata growing system. It could also be used for the "multi-goal" estimation in dynamic monitoring of forest resources with remote sensing technique.