The　refractive　index　sensitivity　of　the　tetrapod　nanostars　was　studied.　The　extinction　spectra　and　environmental　refractive　index　sensitivity　of　the　tetrapod　gold　nanostars　with　different　branch　lengths　were　calculated,　and　it　was　found　that　the　environmental　refractive　index　sensitivity　of　the　tetrapod　gold　nanostars　with　longer　branches　was　higher.　The　environmental　refractive　index　sensitivity　of　the　tetrapod　gold　nanostar　coated　with　a　protein　layer　is　calculated.　The　greater　the　dielectric　constant　of　the　protein　layer,　the　smaller　the　influence　of　the　thickness　of　the　protein　layer　on　the　refractive　index　sensitivity　of　the　tetrapod　gold　nanostar,　but　at　the　same　time　the　tetrapod　nanostars　can　achieve　higher　environmental　refractive　index　sensitivity.　These　sensing　properties　of　the　tetrapod　gold　nanostars　provide　potential　for　nano-optical　biosensing　research　and　provide　theoretical　guidance　for　the　design　of　LSPR-based　biosensors　and　SERS　applications.