Abstract: A method for shock-free wing design using "fictitious gas"concept is comprehensively introduced in the paper.The main points of this method are briefly described. Several fictitious gas laws are presented. A spece-matching procedure adopted in supersonic flow region is concretely explained.The gain in 2-D or 3-D design conditions and off-design conditions is also discussed . Finally, an engineering approach for nearly shock-free wing design is introduced.