Abstract:Larix chinensis,listed in Chinese Plant Red Data Book,is a typical endemic species in Qinling Mountain.It is the only tree species that structures the pure forest locates 2600-(3600 m),which has special functions to conserve water,firm mountain stone and maintain water and soil at the timberline area.We present a model for predicting the diameter at breast height(DBH)growth of L.chinensis.Data for this study were collected in Taibai Mountain Natural(Reserve),Shaanxi Province,China.Four samples of 40 m×40 m were investigated and every plant was stem-mapped.Species,DBH,total height,and crown length were recorded for each tree that had reached a diameter of 5 cm at breast height.Area potentially available index(APA),reflecting objectively the competition and growth pattern of L.chinensis,was selected in this paper.Taking subjective DBH and competition index as independent variables and the two yearly DBH relative growth rate as dependent variable,the growth model was established with good regression result.The r-value was 0.916 and the P value was less than 0.05.The model can simulate and predict the growth for L.chinensis efficiently.