The distribution of interference pattern in Young’s double-slit experiment of vortex beam, which was generated by passing a plane beam through a spiral phase plate, was investigated. It is found that topological charge of vortex beam influences the interference pattern, i.e., by compared with the straight interference pattern of plane wave, the interference pattern of vortex beam is shifted in the transverse direction as we look from the top of the interference to the bottom, and the magnitude and direction of shift are related to the topological charge. The topological charge of vortex beam can be derived from the interference pattern. Vortex beams carrying orbital angular momentum may find applications in information encoding and transmission. Therefore our research results may be applied to this new kind of information encoding and transmission.