A 2 μm waveband GaSb based subwavelength grating mirror is investigated, and the influence of subwavelength grating parameters on reflection spectrum is discussed. The mirror has a wide bandwidth and a high reflectivity with center wavelength of 2 μm in case of TM mode. The ratio of reflection bandwidth to central wavelength is more than 26% when the reflectivity is more than 99%. Especially, reflectivity of the mirror is more than 99.9% at the range of 1.895-2.08 μm, and the bandwidth is 185 nm, while the reflectivity in TE mode is lower than the lasing condition of the vertical cavity surface emitting laser (reflectivity is less than 95%). Each parameter of the structure has bigger fabrication tolerance, which facilitates monolithic integration of vertical cavity surface emitting laser.