As an important ecological boundary, and because of climate change, alpine timberlines have received much attention. The Three Parallel Rivers region is characterized by conspicuous vegetation vertical zonality and is therefore the ideal area to study alpine timberlines in China. Using remote sensing, we obtained classification maps of land use and land cover for the Three Parallel Rivers. The distribution of forest land was extracted from these maps for the alpine timberline. Alpine timberline datasets were checked by visual interpretation and used to analyze the relationship between the spatial pattern of alpine timberline and four geographical factors (slope, aspect, latitude and longitude) systematically. The results showed that the elevation range of alpine timberline in the Three Parallel Rivers was 3 521~4 650m. The alpine timberline was mainly distributed on slopes 15~35°, and rarely occurred in areas with slopes less than 2° or more than 55° . The highest timberline was on acute steep slopes. The spatial pattern of alpine timberline showed significant characteristics: western aspects with higher elevations than eastern aspects, and northern aspects higher than southern aspects. The maximum elevation of the alpine timberline appeared on the northwest aspect; the minimum was the southeast. There was no correlation between the longitude factor and the alpine timberline spatial pattern. However, the spatial pattern was highly correlated with latitude and as latitude increased, the alpine timberline rose. Topographical factors and water and heat conditions were typical impact factors and combined to affect the spatial pattern of the alpine timberline.