Abstract: Metal sheets in periodic structure simulation often contain slit structures, and accurate simulation of such structures consumes large computational resources. In order to solve this problem, this paper draws on the thin wire fast scheme, which equates the slit of the metal sheet to the magnetic flow, thus avoiding the modeling part of it, which can reduce the difficulty of modeling and computation. Examples show that the scheme in this paper has high accuracy and can significantly reduce the computational resources, and its further optimization study can provide technical reserves for related multi-scale problems.