The high resistance and severe optical absorption brought by the traditional P-side distributed Bragg reflectors (P-DBRs) have been the bottleneck of the development of 2.0 μm GaSb based vertical cavity surface emitting lasers (VCSELs). For this reason, a P-side mirror with high contrast subwavelength grating (HCG) is designed and simulated by the rigorous coupled wave analysis method. The testing results show the HCGmirror,easy to make, has 278nm bandwidth with reflectivity more than 99.5% and 148 nm bandwidth with reflectivity greater than 99.9% around the central wavelength of 20 μm for TM mode. Such a mirror can fully meet the requirements of VCSELs, and can effectively avoid the problem of diffraction characteristics deterioration caused by heteroepitaxy and so on.