The compressed gas for ambient temperature in vortex tube can be separated into two streams of different temperature gas, which phenomenon is unapparent for non-compressed gas. However, for non-compressed high-temperature gas, it can produce temperature difference of more than 20°C in vortex tube, which has been ignored by researchers. In this paper, basic principle of temperature difference effect in vortex tube is described firstly, and cooling effect produced by different inlet temperature in the condition of low pressure ratio is analyzed, which results that obvious cooling effect can still be produced for high temperature and low pressure ratio. Combined with factual operation conditions of cyclone separator for circulating fluidized bed (CFB) boiler, a design and renovation method of cyclone separator is proposed firstly according to temperature difference effect principle of high-temperature gas in vortex tube. According to the analysis, the separation efficiency and boiler performance will be enhanced by using temperature difference effect in vortex tube to design and reconstruct the existing cyclone separator.