Using FB805-type rotating liquid experimental instrument，a simple measuring method is designed to explore the law of refractive index of laser light in the same medium changing with temperature．This method can intuitively and real-time obtain the refractive index of liquid at different temperatures，and then obtain the relationship between temperature and refractive index(temperature range is 27．5 ℃ to 80 ℃)．Through the experimental operation，experimental data collection and processing and error analysis．it will provides ideas for the improvement and further exploration of the instrument．