The refractive index of liquid is measured by combining the capillary phenomenon and theMichelson interference principle. Firstly, the relational expression between the speed at which the interferencefringes swallow (or spit out) and the refractive index of the liquid was deduced.In the experiment, a videorecording the changes of the interference fringes swallowing (or spitting out) when the liquid flowed out throughthe capillary tube was made.A Matlab program was written to proeess the data of the video to obtain the speed,and then this speed was substituted into the relational expression to caleulate the relractive index of the liquid.The relative error of the experimental result was 0.76%6,Thus, convenient, fast and accurate measurement of therefractive index of liquid was achieved.