A duct piece assembly device of small-span steel corrugated pipe bridges and culverts comprises a sucking disc hydraulic telescopic arm system, a 360-degree overturn horizontal telescopic arm system, a vertical lifting system, an intelligent control system and a waling and fixing support system, wherein the vertical lifting system comprises a fixing frame, a vertical telescopic cylinder, an oil hydraulic pump and an oil tank; the 360-degree overturn horizontal telescopic arm system comprises a horizontal fixing rack, a horizontal fixing arm, a 360-degree overturn horizontal telescopic arm, a telescopic cylinder, an overturn hydraulic motor and a positioning cover; the sucking disc hydraulic telescopic arm system comprises an electromagnetic sucking disc, a sucking disc hydraulic telescopic arm, a sucking disc hydraulic telescopic cylinder and a positioning assembly; and the walking and fixing support system comprises a horizontal rotating pedestal, a walking system and a fixing support system. The conventional mechanical control and electrical control are adopted, rapid assembly of small-span steel corrugated pipes is realized, the assembly efficiency is raised, and the device is suitable for newly-built small-span steel corrugated pipe bridges and culverts and upgrading and rebuilding projects of old bridges and culverts.