Abstract: In order to measure refractive index of liquid more accurately, one method based on surface plasma resonance wavelength was proposed. The model was built by using Kretschman structure and software simulation was carried out. The experimental platform was set up and the experimental research was carried out. The error between experimental and theoretical results was analyzed. The results show that, when the refractive index changes within the range of 1.33RIU~1.36RIU, the absorption peak of surface plasma resonance produces a frequency shift with the change of refractive index of liquid sample. And its sensitivity is up to 4808.94nm/RIU. Refractive index of liquid can be measured accurately with the method and the system has simple structure and high sensitivity.