To elucidate the influence of laser polarization state on optical trap stiffness, the three-dimensional stiffness of four kinds of optical traps with different polarization states (azimuthally polarized beam, radially polarized beam, linearly polarized beam, and circularly polarized beam) to trap silica beads with different sizes was investigated. The result show that, when the silica bead's size is equivalent to the laser wavelength, the three-dimensional stiffness of circularly polarized beam and linearly polarized beam are larger than those of radially polarized beam and azimuthally polarized beam. With the increase of the silica bead's size, the three-dimensional stiffness of azimuthally polarized beam and radially polarized beam are larger than those of circularly polarized beam and linearly polarized beam. In addition, the experimental results also show that, when using an oil-immersion objective lens to trap particles, the spherical aberration caused by the mismatch of the refractive index of oil and water will reduce the utilization of the numerical aperture of the objective lens. The work reported in this paper provides a guidance and reference to the force measurement when using trapping beams with different polarization states.