In order to study the light intensity and phase characteristics of the composite vortex beam, two zero-order radial Laguerre-Gauss(LG) vortex beams with different topological charges are coaxially superimposed to produce a new type of composite vortex beam. The influence of the topological charge on the light intensity and phase distribution characteristics of the composite vortex beam is theoretically studied, and the linear relationship between the topological charge and the diameter of the central dark spot and the number of bifurcations of the inner and outer rings is analyzed, and numerical simulation is carried out. The simulation results show that when two zero-order LG vortex beams with different topological charge are superimposed, the light intensity distribution shows a pattern of alternating bright spots and dark spots, the number of bright spots is equal to the difference between the topological charges of the two vortex beams, the phase distribution shows a double ring mode, and the bifurcation numbers of the outer and inner rings are determined by the larger and smaller values of the topological charges respectively, which do not affect each other. When vortex beams with the same topological charge number are superimposed, the number of bright spots in the light intensity diagram is four times that of the topological charge number, and the bifurcation number in the phase distribution diagram is the same as that of the topological charge number.