In this paper, three kinds of single frames including 6, 8 and 10 stories are presented using LS-DYNA software, the stability of structure is studied due to the bottom side column demolition. The results show that the more structure floors, the more side span cantilever structure system collapses. The damage of the junction with the main structure is due to gravity bending moment. The main structure swings back and forth in horizontal direction and damage in some parts of the frame. The more floors, the more the period t of range of main structure movement is longer.