This study establishes a multiple degrees-of-freedom structural dynamics analytical model to analyse the influence mechanism of different factors on blasting tight bottom and shape of muckpile. The structural displacement response and distribution of internal forces in the bench rock mass are analysed based on several factors including blasting parameters, explosion load, initiation condition, and geological condition. In addition, the structural failure characteristics of the bench rock mass are studied based on a rock strength criterion. The results indicate that the explosive load strength determines the internal forces of the bench rock mass. The use of blasting parameters with large borehole spacing and small row spacing can increase the internal force and deformation of the bench rock and enhance the effect of the breaking and throwing of rock mass. In addition, the strengthening of the lithology of the bottom rocks or weakening of the lithology of the middle rocks can make destroying the bottom rock mass more difficult and increase the probability of blasting tight bottom formation. Adjusting the initiation point to below the weak-lithology segment of the bench can enhance the internal force and displacement of the bottom rock mass, to improve the blasting effect and avoid blasting tight bottom formation. Combined with the bench blasting field test of the Changjiu limestone mine, it verifies the results of the theoretical analysis of the bench blasting rock mass destruction based on structural dynamics. The results can be used as the theoretical basis and technical support for improving the bench blasting effect.