Abstract: This paper is meant to discuss the relations between the terrain condi－ tions and avalanche activities in the main valley of Gongneisi River on the base of observation data of avalanches for 20 years and some results obtai-ned from interpretation of airphotographs and topographic maps during the period from 1985 to 1986，when avalanche hazards mapping was carried out． It was emphasized to describe the effects of＞-shape orographic terrain of the valley，its east－west strike，stepped erosion surfaces and triangulation areas of slope by the river on the avalanche activity tensity and its time-space distribution，avalanche types and its sizes．