The refrigeration cycle can approach to the Lorenz cycle when using the zeotropic refrigerant mixture because of the temperature glide during phase change. A method based on statistics to select the zeotropic refrigerant mixture was proposed in this paper. The choice of the zeotropic refrigerant mixture depended on the variance of temperature difference between the refrigerant and heat transfer fluid (HTF) in heat exchanger. The smaller the variance was, the closer the refrigeration cycle approached to the Lorenz cycle. Some zeotropic refrigerant mixtures were evaluated in air-conditioning condition using this method. It was found that R407C was the best choice in air-conditioning condition because of its smallest variance.