Based on the Second Fick Law, a mathematical model of mass diffusion was established by using the principle of diffusion process in semi-infinite plate. The maximum interference fringes parameters were determined with experimental method of Laser holographic interference, and the mathematical description of liquid-liquid mass diffusion coefficient was obtained. The maximum value of interference fringes produced by sucrose solution at a concentration of 0.10mol × L-1 diffusing to water was measured at 15℃, and the mass diffusion coefficient of sucrose solution was calculated.The error is 3.67% and the standard deviation is 0.378 comparing to the values in other papers. The result demonstrates the accuracy of the diffusing formula using for the interference fringes maximum point, provides a beneficial reference to the research of mass diffusion coefficient theory for new refrigerants, which is urgently required in chemical engineering application