Leaf area is an important factor for quantifying the potential production of trees because it is closely related to tree growth. The dynamic changes in leaf area directly drive the change of tree growth. At present, scholars hold varying views on the dynamic changes in stand leaf area. Some scholars proposed a classical hypothetical trend that leaf area of a stand showed a more or less constant level after the initial peak. On the contrary, other scholars proposed another hypothetical trend: i.e., the stand leaf area showed a single peak maximum of leaf area followed by a decline after canopy closure. However, neither the hypothesis of constant leaf area nor the hypothesis of a maximum leaf area clearly explained why leaf area should remain constant or decline after canopy closure from the growth models. In this study, data were collected from 54 plots, containing 144 trees in various subtropical climatic zones. We developed tree leaf area and stand density models for Chinese fir using nonlinear mixed-effects models based on six growth equations (Richards, Logistic, Gompertz, Mitscherlich, Korf, Weibull). The stand leaf area was determined by multiplying the tree leaf area by the number of trees. Then we explored the dynamic change of stand leaf area. The results showed that the optimal tree leaf area model (at the plot level) considered the random effect of the plot on the parameter 'a’ of the Logistic function. The optimal stand density model (at the population-averaged level) considered the random effect of the site on the parameter 'a’ of the Logistic function. However, the heteroscedasticity structure of both models was not considered. The dynamic change in stand leaf area followed a unimodal pattern, increasing rapidly during the young growth phase, peaking, and then gradually declining at a slower rate. With the consideration of self-thinning as a premise, from the growth model perspective, the dynamic change in stand leaf area exhibited a unimodal pattern, instead of remaining constant after reaching its peak. In addition, the decrease of stand leaf area after reaching the peak was caused by the decrease of stand density. Therefore, a series of management measures can be considered to delay the decline time of leaf area in forest, so that the forest can maintain a high production volume for a long period of time, so as to obtain greater ecological and economic benefits. Our findings are of great significance for the quantitative management of Chinese fir plantations in different climate zones.