The invention discloses a method for drop point selection and capacity configuration of a flexible DC back-to-back device. The method includes: determining an initially configured line of the flexibleDC back-to-back device by calculating the power transmission capacity of a dual-dual channel cross-section after configuration of the flexible DC back-to-back device; determining the determined configuration line and capacity of the flexible DC back-to-back device by calculating the short-circuit current of busbars on both sides of the dual-dual channel section after configuration of the flexibleDC back-to-back device; and determining the configured busbar side of the flexible DC back-to-back device by calculating the voltage sensitivity of the busbars on both sides of the dual-dual channelcross-section after configuration of the flexible DC back-to-back device. By constructing a flexible DC back-to-back device at a certain side busbar of the existing dual-dual loop cross-section, cross-section tidal current distribution can be optimized, the overall power transmission capacity can be improved, and the short-circuit current of the busbars on both sides of the cross-section can be reduced, and the auxiliary voltage reactive power support capability can be provided.