According to Lorentz theory of electrons and Beer-Lambert law

a theoretical model for describing the linearity relation between the solution concentration and its refractive index was proposed.To examine the validity of the theoretical model

the sodium chloride solution and the sucrose solution of distilled water were studied experimentally.Based on the experiment data and the least squares method

the experimental models between the concentration and the refractive index of the measured solutions were set up.The results indicate that the error between the theoretical and the experimental model is 2%.The research is useful for the determination of solution concentration by surface plasmon resonance and thin-film enhanced Goos-Hnchen shift.