This　paper　presents　the　design　and　numerical　simulation　of　vertical-cavity　surface-emitting　laser　(VCSEL)　incorporating　a　high-contrast　grating　(HCG)　by　using　a　three-dimensional　(3-D)　finite　difference　time　domain　(FDTD)　method.　The　polarization　dependence　of　HCG　parameters　as　well　as　HCG　reflector　properties　are　numerically　studied.　We　investigate　the　resonant　spectra　behavior　and　modal　properties　with　respect　to　different　aperture　size.　Furthermore,　the　quality　factor　(Q　factor)　related　to　modal　loss　is　calculated,　and　is　used　to　explain　the　mode　selection　of　the　HCG-VCSELs.　Based　on　the　simulation　and　analysis,　it　is　found　that　the　designed　HCG-VCSELs　exhibit　larger　mode　discrimination　compared　to　the　conventional　VCSELs.　Our　work　could　provide　guidelines　for　designing　and　optimizing　polarization-stable,　single-mode　VCSELs　for　use　in　chip-scale　Cs　atomic　clocks.