Abstract: In order to study the dynamic failure characteristics and dynamic damage characteristics of coal rocks, using split Hopkinson pressure bar(SHPB) and stress loading system, impact tests and uniaxial compression experiments were performed on coal rock samples. According to the characteristics of stress-strain experiments curve, based on the overstress model, continuous damage theory and statistical strength theory are applied to establish an overstress damage model suitable for the dynamic characteristics of coal and rock. The results show that under dynamic load, when the strain rate is small, the coal rock crushing method is similar to that under static load; as the strain rate increases, the dynamic load failure strength increases significantly, and the dynamic modulus increases first. It remains the same after being large, the plastic deformation increases first and then decreases, and the stress-strain curve has obvious plastic flow characteristics; the experimental curve is fitted using the established constitutive equation of coal rock overstress damage model, and the comparison between the two verifies the correctness of the model.