Because alpine timberline is a kind of ecotones which is highly sensitive to disturbances and environmental changes, it has become a major focus of global climate change research. Larix chinensis is a timberline trees species on Mt. Taibai in the Qinling Mountains. It is densely distributed on Mt. Taibai and plays an important role in environmental protection in the high altitude zone. The forest near timberline was divided into three transects, i.e., below timberline, at timberline and at tree line. Regression equations between DBH（diameter at breast height）and age were established in the three transects, and ages of other trees were calculated. The results indicated that: (1) There were significant differences in most of investigated characteristics, such as average diameter at stem base, average DBH and average height, between different altitudes near timberline (P<0.05). These characteristics decreased with the increase of altitude. (2) The regression equations between age and DBH of trees in the three transects were statistically significant (P<0.05), but the relationships between age and DBH of height of tree were poor. (3) Multi-modal age distribution was found in the three transects. We propose that limiting environmental factors, e.g. temperature, play an important role in determining the age structure of L. chinensis populations near timberline; (4) Most individuals of different age classes had a clumped distribution at different scales. With the increase of population age, the distribution pattern had a trend from clustering to random, and the clustering intensity decreased somewhat.