In　order　to　measure　the　group　refractive　index　and　thickness　of　birefringent　crystals　simultaneously,　a　method　based　on　spectral-domain　interferometry　is　proposed.　The　optical　path　of　each　reflection　layer　of　birefringent　crystal　is　converted　into　spectral　interference　fringe　of　corresponding　frequency　by　the　principle　of　spectral-domain　interferometry,　and　the　accurate　optical　path　calculation　is　realized　by　fast　Fourier　transform　and　Hanning-windowed　energy　centrobaric　method.　A　two-step　measurement　method　was　designed　to　measure　the　crystal　thickness　and　group　refractive　index　of　ordinary　(　o　)　and　extraordinary　(　e　)　light　synchronously　by　comparing　the　changes　of　the　optical　path　before　and　after　the　insertion　of　the　sample.　The　comparison　between　experimental　and　theoretical　results　of　LiNbO3　crystals　shows　that　the　accuracy　of　the　thickness　measured　by　this　system　is　better　than　1　mu　m　and　the　relative　error　of　the　group　refractive　index　is　better　than　0.15%.　The　measurement　method　is　simple　to　implement　and　has　high　precision,　which　is　of　practical　significance　for　realizing　the　rapid　and　high-precision　measurement　of　optical　parameters　of　birefringent　crystals.