Abstract: The deforming-cracking mechanisms of strong pulling-apart in south-north direction, weak pulling-apart in east-west direction ,and anticlockwise rotation on the horizontal were been recognized after analysis of distribution of coal mined-out area, geopressure action on the roof, and rock body fracturing and deformation in last twenty yeas in this article. On the above analysis,the authors made a series of calculations and applied them to engineering design for controling the Lianzi Cliff dangerous rock body.