Abstract: In order to analyze the mechanism of rib spalling of hard coal seam with developed beddings,the site observation and theoretical analysis and laboratory experiment were applied to research the influence of rib stability of physical and mechanical properties and joints and fissures distribution of coal. The control technolog y of rib spalling by water injection with ultra high pressure was proposed. The results showed that rib spalling of hard coal with transversely developed beddings often 0 ccurred on the bedding planes and the failure modes were dominated by tensile fracture. Increased water injection pressure could enlarge wetted radius of hard coal se am and shorten of water injection time and enlarge the hole spacing. The application of this technology could reduce the occurrence of largesized coal obviously and im prove the operating rate and effectively relieve the rib spalling and accelerate the advance speed.