Abstract: This　paper　presents　a　simple　method　to　measure　the　refractive　index　of　liquid　by　laser.According to　the　vertical　prism　angle　of　the　square　container，when　the　total　reflection　crosses，the　incident critical　angle　can　be　measured，that　the　liquid　refractive　index　can　be　calculated.Then，combining　with　the Cauchy's　empirical　formula，the　dispersion　rate　of　the　liquid　can　be　calculated　by　using　the　relationship　between the　refractive　index　and　the　critical　angle.

Key words: vertical　prism　angle, total　reflection, refractive　index, Cauchy's　empirical　formula, dispersion　rate