About 20% fluorine atoms recombine to fluorine molecules in continuous wave(CW )DF/HF chemical laser’s nozzle, and it is one of the most important factors influencing the bumping efficiency and lasing intensity of lasers. The fluorine atoms loss is caused mainly by wall recombination. Nozzle contour design does not have an obvious effect on reducing it. Combining the gaseous film cooling used in aerospace realm, a new kind of nozzle is designed by injecting helium film from nozzle’s converge section. The film is estimated to be a separating layer between the main stream and nozzle wall which can reduce fluorine atoms loss, protect the wall, and throat region from ablation. The numerical results show that the protection and frozen efficient are obvious. The helium film occupies part of the stream channel, which influences the main stream’s transportation. The absolute mass flow rate of fluorine atom falls at nozzle exit plane(NEP) if the main stream’s property keep constant. Several methods are presented to improve the design’s inherent shortage.