Abstract: Since Epstein realized the energy conversion between light and heat and got the net cooling capacity in 1995,this refrigeration method has been developed very rapidly because of its merits,such as mini volume,light weight,free electromagnetic radiation,non-noise,high reliability.In the meantime,anti-Stokes fluorescent cooling has luring future in military,aerospace,satellite,micro-electronics,cryogenic physics and engineering.The basic thermodynamic laws are utilized to analyze the conversion depth about heat energy into light radiation in detail;the definitions of light effective temperature and thermodynamic conversion efficiency are introduced.Then a formula to calculate the thermodynamic upper efficiency limit has been derived,which can provide a design guide rule to produce the laser cooling machines.