Since 1950, 700 plots were established in the alpine and canyon region of western Sichuan. The distribution characteristics and the relationships between forest succession and environmental gradients were studied. The results show ed that the main tree species were Picea and Abies in this region, and there were more than 90 forest types. Abies forests mainly distributed in the middle and upper reaches of rivers and their branches, and Picea forests mainly distributed in wide valleys and on half-shaded and half-sunny slopes. The natural regenerat ion was poor under primitive spruce and fir forest canopy, but was good in the spruce and fire forestgap. The relationship between forest succession and vertical gradient was closely related to the relationship between forest succession pr ocession and plant synusia under primary forests. Human activities could promote and postpone succession process. The results of expanding regeneration were often influenced by topography, vegetation and wind direction.