At present，there is no special lightning protection standards of designing, construction, and testing aimed at metro systems in China，so that there is no systematical technical standards in lightning protection of metro systems launched in China. An analysis is made of the main ways and approaches in which metro systems are attacked by lightning, and the necessity of lightning protection for metro systems is discussed. On the other hand, aiming at the key point of lightning protection for metro systems, according to the calculation of theoretical analysis, it is assured for the first time that the lightning protection of metro systems should be classified as Class 2，and the key parameter of metro Lightning protection—theoretical value of earthing resistance—is deduced. From the aspects of five elements such as the lightning arrester， earthing， equipotential connection, shield， composite wiring, and surge protection, specific measures of metro lightning protection are analyzed, which can provide references for those who are engaging in designing, construction, and testing of lightning protection for metro systems, and be useful for the formation of technical standards of lightning protection for metro systems.