The invention provides an operating method for changing duplex V chain composite insulators on live line of an extra-high voltage DC line. The method comprises the following steps: (1) transmitting a first transmitting rope to a cross-arm tower, arranging a transmitting rope fixing point on the first cross iron position of the side of a cross-arm tower body, installing a transmission system; (2) installing an insulator; (3) dismounting a stringing lead screw and a large blade clamp, transmitting an insulating rod to ground; dismounting a pulley block and a basket system, transmitting the pulley block and the basket system to the ground; recycling a protection rope and other tools and materials on the tower; taking up the first transmitting rope so that the first transmitting rope becomes a single rope; and getting down the tower. The operating method for changing duplex V chain composite insulators on live line of an extra-high voltage DC line is simple and clear in program, and operation procedure can be preferably monitored. The method can effectively speed up commissioning construction of +-800 kV DC extra-high voltage DC lines, and greatly improves working efficiency.