Because circularly polarized vortex beam can be characterized as the linear super position of radially polarized and azimuthally polarized components in the cylindrical coordinate, when study the focusing properties of the circularly polarized vortex beam, we must consider radially polarized vector beam with topological nuclei has azimuthal component after focusing and azimuthally polarized vector beam has radial component after focusing. Based on the corrected tightly focusing formula of the circularly polarized vortex beam, we afresh study the tightly focusing properties of the circularly polarized vortex beams with different topological nuclei. The results show that not only the focusing of the single handedness of the circularly polarized vortex beam but also the focusing of superposition of two circularly polarized vortex beams can generate flattop beam. By choosing the proper amplitude ratio, waist radius and the aperture blocking, the half-width of flattop beam can be changed effectively.