Abstract: Rockfall hazard is a common type of geological hazard in mountain areas. It has significant meaning to research the character of rockfall for geological hazard investigation and risk assessment. A rockfall hazard occurred on 2018.9.15 during a project in Nepal. We investigated it at site and analyzed its genesis to find out the reason of the accident. The investigation results showed that"9.15 event" is a natural geological disaster and is not affected by human activities. The main cause of the accident is that the scope of rockfall from super high slope exceeded the scope which was predicted in the early stage. There are so many uncertainties in the rockfall movement. The movement pattern of rockfall has been predicted through the imprint analysis at site. According to impact point surface morphology, slope deposit material and geometrical characteristics, we calculate and analyze the motion trail and motion process of rockfall by the kinematics theory. In addition, combined with the scale of rockfall source area and the size, shape, mechanical properties of the rockfall blocks, we apply the Rocfall software to simulate and analyze the rockfall trail of super high slope. The Rocfall can calculate the energy of rockfall and provide the reliable basis for protection measures. The opening curtain type net has a good effect on preventing from high and steep slope rockfall disaster. This paper is useful to the investigation and prevention of dangerous rock of other similar height and steep slope, as reference.