Half-wavelength AC transmission technology is attracting more and more attention worldwide owning to its unique economic and technological advantages. Its history of development and current research is reviewed and the fundamental transmission characteristics of the technology are discussed. A detailed analysis is made of such crucial technical issues as the optimization of the man-made tuning network， power transmission and transient stability， operation and maintenance of the lines， secondary arc and its suppression， internal over-voltages as well as load supply along the transmission lines. The future trends of half-wavelength transmission technology and referential suggestions are also outlined.