The invention provides a walking type construction device used for steel truss girder incremental launching and a construction method thereof and belongs to the technical field of steel truss girder construction. The structure of the walking type construction device used for steel truss girder incremental launching comprises a walking type jack, a mobile pad body, a mobile system and adjusting sheets; the walking type jack is arranged on a concrete rest pier; the adjusting sheets are arranged in positions, on the two sides of the walking type jack, on the concrete rest pier; the mobile pad body is arranged on the upper sides of the adjusting sheets; a steel truss girder is supported at the upper end of the mobile pad body; and the mobile system is fixed at one end of the mobile pad body. The construction method comprises the following steps of (1) hoisting and placing the device; (2) enabling the walking type jack to incrementally launch a pad beam to drive the steel truss girder to move forwards; (3) enabling a supporting sleeve to cross over supporting blocks; (4) enabling the pad beam to move to the right for a pitch; and (5) enabling the supporting sleeve to move to the right for a pitch. The walking type construction device used for steel truss girder incremental launching is used for solving technical problems that the steel truss girder is unevenly stressed during incremental launching and the concrete rest pier generates bending moment.