Abstract: In order to find the relationship between the refractive index and the volume fraction of acetic acid solution and alcohol solution, the principle of optical total internal reflection was chosen to measure the refractive indexes of glacial acetic acid and alcohol with different volume fractions and to obtain their relative curves. The experiments showed that the relationship between the refractive index and the volume fraction of acetic acid solution and alcohol solution was similar to the parabola. It was not the simple linear relationships. The refractive index became larger at the beginning as the solution volume fraction increased, and there was a maximum of the refractive index at a certain volume fraction. Acetic acid solution near the volume fraction of 0.90 and alcohol solution near volume fraction of 0.80 had the maximum refractive indexes respectively. The results are helpful to the comprehensive cognition of the relationship between the refractive index and the solution volume fraction.