Based　on　the　principle　of　total　internal　reflection,　a　new　experimental　system,　in　which　the　sample　is　close　sandwiched　between　two　prisms,　was　designed　to　determine　the　refractive　indices　of　biotissues　and　homogeneous　medium.　Some　mammalian　tissues　have　been　determined　at　laser　wavelengths　of　0.488,　0.6328,　1.0795　and　1.3414μm,　respectively,　and　their　dispersion　equations　have　been　obtained.　And　the　absolute　error　between　the　n　calculated　from　the　dispersion　equation　and　the　measured　is　within　0.002.　By　utilizing　these　dispersion　equations,　the　refractive　indices　of　the　tissues　can　be　obtained　at　any　wavelength　within　the　waveband　of　0.488-1.3414μm.　The　method　has　great　reliability　and　accuracy,　and　it　can　be　used　for　measuring　the　refractive　indices　of　biotissues　and　any　other　medium.