Abstract: On January 27, 2006, a rockfall happened at Yaoyanjiao of Houchang town in Weining county, Guizhou province. Yaoyanjiao high-steep slope has overlying strata covered by carbonate and underlain with soft rock. It also has nearly horizontal coal seams. Based on the analysis of disaster characteristic and process, the conceptual model of generation mechanism is established. There are several deep dissection dissolution cracks and horizontal caves caused by intense karst in high-steep slope. High-steep dyke is therefore formed in high-steep slope. The excessive mining of coal seam from the deep of slope body to slope surface has resulted in high stress concentration in the lower part of dyke and developed into failure. Quantitative analysis of generation mechanism and process is conducted by the employment of MIDAS/GTS software. Further analysis of critical safe distance of mining face from cliff face is done at different recovery ratios. The results can provide reference for analogous conditions of coal mining.