The　mode　splitting　induced　by　electro-optic　birefringence　in　a　P　-　I　-　N　InGaAs/GaAs/AlGaAs　vertical-cavity　surface-emitting　laser　(VCSEL)　has　been　studied　by　polarized　electroluminescence　(EL)　at　room　temperature.　The　polarized　EL　spectra　with　E　[110]　and　E　[11¯0]　directions,　are　extracted　for　different　injected　currents.　The　mode　splitting　of　the　two　orthogonal　polarized　modes　for　a　VCSEL　device　is　determined,　and　its　value　increases　linearly　with　the　increasing　injected　current　due　to　electro-optic　birefringence.　This　article　demonstrates　that　the　polarized　EL　is　a　powerful　tool　to　study　the　mode　splitting　and　polarization　anisotropy　of　a　VCSEL　device.　©　2014　Chinese　Physical　Society　and　IOP　Publishing　Ltd.