The theory background of temperature extrapolation method usually used for heat of fusion measurement of ice is elaborated based on Newtons law of cooling. The corresponding Matlab codes are provided and applied in data processing of experiment results measured by digital thermometer. Regarding to the obtained temperature-time graph, the area-equavalence requirement of the method can be ensured and the results are obtained in expected accuracy. It is found that the approach is insensible to ice and water masses as well as the ice-casting temporature, while the ambient temperature although affects the measurement of thermal convection coefficients, has little effects on temperature extrapolation as well as the corresponding results.