Abstract: Based on the similar irrelative model of forest ecological benefits,the study analyzed the subordinate relations of numerous ecological benefits,and introduced end genetic variables Y₁ and Y₂ as the independent variables of another ecological equation to construct consociation equation set model.Leading from the forest's water absorption benefits,it deeply depicted the dependent and subordinate relations between the forest ecological benefits dependent variable set.Staring from the basic rule of forest ecological benefits,constructed the consociation equation set structure parameters matrix B and Γ restricted by parameter to get linear limit equation HA=L,which is the key to the forest ecological benefits consociation equation set.Especially,the study on the non-linear relation of forest ecological benefits dependent and independent variable was the foundation of forest ecological benefits consociation equation set.The model was excessiveness identified and error structure matrix,not cross matrix.The forest absorbing water and stabling soil and keeping fertilizer and defending sand benefits estimate equations were gotten through the three steps least square estimation method with Matlab program,and the average precision was morn than 80%.From this method,the whole country forest absorbing water benefit was estimated as 4.7×10⁸ t,forest fixing soil benefits was 39×10⁸ t,forest keeping fertilizer benefit was 4.7×10⁸ t and defending sand benefits was 22.8 ×10⁸ t.

Key words: Forest ecological benefits, Consociation equation set, Excessiveness identification, Three steps least square estimatation