The invention provides a rapid calculation method for the electromagnetic scattering characteristic of a periodic-like structure target. According to the technical scheme, the rapid calculation method comprises the steps that in the steps 1-3, special triangulation processing on the periodic-like structure target and RWG function establishing are conducted, wherein the steps are conducted for enabling discrete functions of different submodules to achieve correlation to be capable of being reused; in the step 4 and the step 5, the discrete functions of different submodules of the periodic-like structure target are established; 6, the electromagnetic scattering characteristic of the periodic-like structure target is calculated through the discrete functions established in the step 4 and the step 5. The rapid calculation method is used for the periodic-like structure target, the discrete function establishing process does not need to be repeated multiple times, the discrete functions of all the submodules can be obtained only by conducting coordinate transforming on the discrete functions established for the smallest submodules, and therefore the calculation efficiency is greatly improved. According to the rapid calculation method, the implementation mode is simple, and the calculation precision of an algorithm is not influenced.