Abstract: In the post-peak plastic deformation process of coal and rock materials after failure, the strength parameters gradually decline and the bearing capacity of the material structure declines, which leads to the instability of the coal and rock engineering structure. In the view of the problem in attenuation of structural strength and bearing capacity of layered roof which effects safety and stability of roadway, to reveal weakening process of bearing capacity of bearing beam structure from macroscopic perspective, the method of revealing the essential relationship of bearing capacity weakening of coal engineering structure was proposed based on the attenuation law of equivalent macro-strength parameters. The attenuation model of structural bearing capacity was established. Moreover, the attenuation law of structural bearing capacity was analyzed by FLAC numerical calculation program. The results show that the variety law was obtained that the equivalent macro-strength parameters of cohesion and internal friction angel were attenuated in the form of cubic polynomial function with the increase of normalized interval variable δ of plastic shear strain.