The competition-density (C-D) effect in Cunninghamia lanceolata stands was analyzed by using the reciprocal equation 1/omega = A rho + B, where omega and rho represent mean stem volume and density, respectively, the C-D curve given by the reciprocal equation on logarithmic coordinates shifted upward with time. With the increase of physical time t the biological time tau defined as the integral of lambda (t), the growth coefficient in general logistic growth curve, tended to increase to the maximum. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. With increasing tau, the coefficient A increased abruptly up to a maximum value, and then tended to decrease gradually to a constant level, whereas the coefficient B decreased exponentially, and tended to close to zero. The coefficient of growth lambda (t) decreased with increasing stand age.