The invention discloses a lightning protection system of an ultra-high voltage alternating-current double-loop circuit. The system comprises an ultra-high voltage alternating-current double-loop tension-resistant tower (10) and an ultra-high voltage alternating-current linear tower (1). The best ultra-high voltage alternating-current double-loop circuit lightning protection model is determined through different arrangement and combination of an OPGW (optical fiber composite overhead ground wire) optical cable or earth wire (6), a V-shaped suspension string (7), a suspension string (8) of the OPGW optical cable or a lightning wire, and a tension-resistant string (9) of the OPGW optical cable and the lightning wire, wherein an upper layer of cross arm (2) and a middle layer of cross arm (3) of the ultra-high voltage alternating-current linear tower (1) are laterally hung to the OPGW optical cable or the earth wire (6); and the upper layer of cross arm (2), the middle layer of cross arm (3) and a lower layer of cross arm (4) are downwards hung to the V-shaped suspension string (7) and a multi-splitting lead (5). The system can effectively prevent shielding lightning and is high in lightning protection effect.