The invention discloses a single-arm folding inserting type extra-high-voltage direct-current disconnecting switch which comprises two monopoles which are structurally identical and realize synchronous operation through electric linkage. Each monopole comprises an electric operating mechanism (1), a transmission connection rod (2), a foundation support (3), a triangular fixed underframe (4), an operation insulator (5), a supporting insulator (6), a transmission base (9), a lower conductive pipe (10), an upper conductive pipe (12), a moving contact finger (13) and a static contact (14). A main conductive pipe in opening and the static contact form an isolating fracture in a horizontal direction, and the main conductive pipe in closing pushes the lower pipe to be in circular motion from top to bottom through the connection rod and simultaneously drives gears and racks to move to enable the upper pipe to be in reverse motion to enable the moving contact to be meshed with the static contact, and on the contrary when opening. The single-arm folding inserting type extra-high-voltage direct-current disconnecting switch has the advantages of stability and reliability in motion, small operating force, small closing impact, high through-flow stability, good corrosion resistance, long service life and the like.