The tightly focusing property of vector beams with off-axial polarization singularities are numerically investigated, according to the Richard-Wolf vector diffraction intergation theory. A method for designing speical focal field is proposed, based on the tightly focusing of vector field with generalized polarization distribution, after analyzing the tightly focusing of radially and azimuthally polarized beams. Moreover, the modulation effect of symmetric broken of off-axial polarization singularites on the focused field, especially the modulation effect on the Spin Angular Momentum (SAM) density, are discussed by analyzing the variation of SAM distributions arising from spin-orbital coupling. The results not only rich the tightly focusing property of vector beam, but also provide reference for improving the distribution of focal field.