Based on strata movement and ground pressure analysis, this paper presents a relationship between hard main roof movement and floor cracking. The results show that pre-cracking hard main roof before its first cracking, the depth of floor cracking will be greatly reduced. Subsequently, the possibility of underground water ingress will be greatly reduced. This conclusion is applied at many longwall faces in Jiaozuo Mining area. The field monitoring data show that the average ingress water volume is decreased from 100 to 30 m3/h after pre-cracking hard main roof. The result in this study can be used in other mining areas with similar conditions.