We present the single-slit diffraction of the arbitrary vector fields with different parameters m, n, and f0 theoretically and experimentally. The single slit covers the polarization singularity in the center and therefore the influence of the polarization singularity on the diffraction fringes is analyzed. The experimental results which agree well with the simulation results show that the total intensity of the diffraction field is related only to the topological charge m, but the polarization distribution of the diffraction field is related to all the parameters m, n, and f0. Therefore, the diffraction patterns allow to determine all the parameters of the arbitrary vector fields.