The beam with helical phase distribution has Orbital Angular Momentum(OAM), whose helical phase depends on the topological charge of OAM state. The phase distribution and the light field distribution of the superposition vortex beams were analyzed theoretically, and then the phase distribution pattern was loaded onto the spatial light modulator to generate the superposition vortex beams. The light of the field diffraction pattern with different topological charges superposition was discussed. The experimental results show that the optical field diffraction pattern of the superposition state varies regularly with the positive and negative values of the superposition of the beam topological charge and the numerical value, namely when the superposition of two optical topological charges is different symbol, the number of diffraction spots is the sum of the absolute values of the two optical topological charges; when the superposition of two optical topological charges is same symbol, the number of diffraction spots is the absolute value of the difference between the two optical topological charges. By this property, the topological charge of the vortex beam can be detected, which provides a new method for the topological charge detection of the superposed vortex beams in the free space optical communication system.