Based on the empirical formula of liquid concentration and refractive index at room temperature，the home experiment of liquid concentration measurement by transmission interferometry is designed． With the principle of wedge equal thickness interference，the size of interference fringes in air and liquid is calculated，respectively．Then the liquid refractive index is calculated by the ratio of the stripe intervals in air and in liquid．In the experiment，self-made trapezoidal glassware，lens，thin paper，beaker，measuring cylinder，semiconductor laser pen，computer and CCD camera are used．The liquid concentration can be measured by equal thickness interferometry．The experiment shows that the experimental results are consistent with the empirical formula，and the experiment can be used as a supplement to the online experimental teaching project．