The heat flows of a series of sodium chloride aqueous solutions contained 21 molar ratios b are measured and analyzed by differential scanning calorimeter in the range of - 50 ～ 50℃. All measured solutions except water appear two endothermic peaks. The peak positions of both move to each other with the increase of b，at the same time，the intensity of high temperature peak decreases and the one of low temperature peak increases. At last，two peaks are gradually overlapped. A method to separate overlapping double peaks is proposed and the b dependent characteristic parameters of melting peak are obtained，which are consistent with the micro - phase separation model. Finally，the spatial distribution of sodium chloride aqueous solutions concentration is given. This research will provide a certain reference to deeply understand the microcosmic structure of the sodium chloride in aqueous solution and solid - liquid phase transition.