Abstract: 【Objective】Basal area is one of the most important forest structure variables, since it is highly correlated with growth and yield at both tree and stand levels. In this study, four methods that are commonly used to estimate basal area were evaluated and compared to create basal area models, and to determine an optimal estimation method.【Method】Measurements of basal areas, perimeters and diameters at different heights of the stem were collected from Chinese fir trees(Cunninghamia lanceolata)using GIS geometrical calculation functions. Models of basal area and perimeter were then created to retrieve the circumference ratio, which was combined with the optimal statistical method for practical applications. 【Results】The statistical relationship between basal area(G)and perimeter(C)was G = 0.077 666 3C² with a coefficient of determination(R²)of 0.998 5. The circumference ratio(F)of Chinese fir was 3.218 899 32, which was found to be larger than the circumference ratio of an ideal circle(π=3.141 592 6). The accuracy of the geometric mean diameter was shown to be highest among the four methods. The statistical relationship between basal area and the geometric mean diameter(d)was fitted as G = 0.817 7 d^{1.990 2}(R²= 0.990 5). Basal areas calculated using F were larger than those calculated using π. The bias of the former method was positive, and that of the latter method was negative. Using the mean of F and π as the circumference ratio, we achieved the highest accuracy and stability of basal area predictions.【Conclusion】We concluded that estimating basal area with a combination of geometric mean diameter and the mean value of F and π is preferable for practical forestry applications.