Abstract: sample plots of Cunninghamia lanceolata stands withvarious site type,age and density,at an elevation of 200～800 m in Jinhua of Zhejiang Province were measured.Taking the highest-production of increment as a goal and screening 42 sample plots as rational density sample plots for regressive analysis through comparison,the mathematical model among mean DBH(D),density(N)and age of stand(A):D=0.458 6 1n(1 500 A/N)-2.769 4 and the mathematical model among mean DBH(D),relative site class(Ps)and age of stand(A):D=2.842 5+0.6970 Ps×A was established.In the condition of different site type and age of stand,the mathematical model among rational stand density of highest-production of increment(N),DBH(D),relative site class(Ps)and age of stand(A)were presented as follows:N=4320.18-161.25 D-46.43 In Ps×A;N-4232.25-164.1 D.Using these models,the rational stand density,interval of intermediate cutting,growing stock etc. can be worked out.