Abstract: Crown inclination is the consequences of that the biological and its environmental factor synthetically influencing the exterior shape of crown.The crown inclination phenomenon and its influencing factors were investigated in this paper in the border trees of Pinus yunnanensis gaps in the mountain area of southwest of Sichuan Province,southwestern China.The crown inclination phenomenon is a general feature in the border tree of P.yunnanensis,the individual amount of crown inclination degree was bigger than 0.5,reached 95%(crown inclination 1(shorted as RCI-1),averaged as 0.72±0.14(n=291,0.231~1)) and 93%(RCI-2,averaged as 0.86±0.37(n=291,0.134~2.583)).Under the natural conditions,the orientation of P.yunnanensis crow inclination probably related to azimuth,and there were near 80% border trees,which were west orientation including southwest and northwest,implying that the degree of crow inclination related to the non-biological factors such as topography and light.The degree of crow inclination of the border trees of P.yunnanensis gaps was influenced by individual feature and neighborhood distribution.The RCI-1 significantly related to DBH,age,lateral tree intervals and back tree intervals,but not related to height and low branch height of border trees;the RCI-2 was only obviously correlated with lateral tree intervals,not with DBH,height, age,low branch height and back tree intervals.Therefore,the degree of crown inclination of the border trees of P.yunnanensis gaps is influenced by individual feature,neighborhood distribution and non-biological environment.