Abstract: To study the macroscopic strength and microscopic crack development and propagation characteristics of coal rock combination body,the discrete element method is used to analyze the strength and failure behaviors of coal rock combination body under different strength ratios.The results indicate that when the coal body structure is weak,the load-bearing capacity of the combination body is relatively low,and the strength characteristics are also the lowest;As the structural properties of coal body increase,the load-bearing capacity of the combination body increases relatively,and the crack initiation stress,peak value strength,peak value strain,and elastic modulus of the combination body also gradually increase;When the coal rock strength ratio is 0.1,the acoustic emission events are relatively continuous.As the coal rock strength ratio increases,the number of AE events gradually disperses,and the maximum number of acoustic emission events also gradually increases;The crack initiation positions of coal rock combination body samples are all located within the coal body structure.When the strength difference between coal body particles and rock particles is large,coal body failure leads to overall instability of the sample.When the strength difference is small,cracks can penetrate the rock.