Because of the complex geological environment in mountainous area, rockfall has become one of the common geological hazards, and it is also the weak link of research. Previous studies have analyzed and discussed many aspects of rockfall. However, the research on the problem of rockfall disintegration caused by the whole failure of rockfall has been neglected. The disaggregation behavior of rockfall in the process of instability is the key to predict the influence range and control effect of rockfall. Therefore, this paper takes the rockfall of tunnel portal slope along Yiwan section of Zhengzhou—Wanzhou high -speed railway as the research object. From the point of view of structural plane, the caving failure characteristics of slope rockfall are examined. Based on the investigation of 15 tunnel portal slopes, the development and distribution laws of rockfall in the study area are firstly summarized from three aspects: slope gradient, lithological association and height difference. Then, according to the structural characteristics of slope rockf mass, the failure modes of rockfall are analyzed. Based on the corresponding relationship between the volume and shape of the upper dangerous rock and the lower falling rocks of the slope, the caving failure evolution process of the slope rockfall is further discussed, the motion features of the rockfalls are finally predicted and analyzed with the simulation software Rockfall. The results show that (1) the upper part of the slope is steep and the lower part is gentle in the study area. The upper bedrock is bare and the slope gradient is basically over 70°. Dangerous rocks are mainly developed in weakly weathered limestone and dolomite. Slope height difference is between 150 and 300 m. (2) Dangerous rock in the upper slope will gradually slide along the basal sliding plane or fall along the tension crack in a stepped mode. (3) The main caving damage mode of slope rockfall in the study area is that the rock masses in the upper slope disaggregate along the structural planes. (4) The rockfalls at most tunnel entrance slopes are highly dangerous. These dangerous rocks may threaten the safety of tunnel entrance. Therefore, it is essential to take appropriate measures for prevention and cure. The research results can provide reference for effective prevention and control of dangerous rock in Yiwan section of Zhengzhou -Wanzhou high -speed railway tunnels under construction.