The invention discloses a catenary sealing device for a subway section partition door and a construction method. The catenary sealing device comprises a sealing plate main body, a moving plate group,an upper pressing plate, a catenary busbar, an elastic rubber block and a sealing strip; the sealing plate main body comprises a bottom beam and a panel; a first notch is formed in the panel; the moving plate group is inserted into a gap of the sealing plate main body, and comprises a moving plate, a connecting frame, a pressing strip and a rolling shaft; a V-shaped second notch is formed in the moving plate, and a first arc-shaped groove is formed in the bottom of the second notch; the pressing strip is connected into the second notch of the moving plate in a pressing mode; a second arc-shaped groove is formed in the bottom of the pressing strip; the upper pressing plate in inserted into the pressing strip, and a third arc-shaped groove is formed in the bottom of the upper pressing plate;a first pore channel is formed by splicing the third arc-shaped groove and the second arc-shaped groove; the elastic rubber block in inserted into the first pore channel; a second pore channel is formed in the elastic rubber block; and the catenary busbar is inserted into the second pore channel. According to the catenary sealing device, the technical problems that a traditional catenary busbar is not tight in sealing, inconvenient in operation and large in space occupation, and cannot be used when the side wall of a tunnel is thin are solved.