Abstract: The cranny of noumenon and carrier of the ruins of Jiaohe was studied using the theory and method of geological engineering and architecture.The cranny included the unloading cranny,tectonic cranny,deformation cranny and construction cranny.There were three groups of preponderant joint plane.The unloading cranny was distributed primarily in the east precipice and wide noumenon with large aperture and long extension as well as largest destructibility.The construction cranny was the main morbidity of wall,and the deformation cranny was the shape of failure of cave.The cranny of carrier was closely related with tiny geography and geological condition,and the characteristics of cranny of precipice were the common effect of the unloading cranny and the joint plane.