The invention discloses a device for aligning cut ends of stirrups in reinforcement cages in modern prefabricated construction engineering; the device comprises a base; two winding supports are arranged on the base face to face, and a winding barrel component is mounted between the two winding supports; a supporting member is arranged on the base and comprise two retractable parts, each retractable part is provided with a rebar head clamp seat, one rebar head clamp seat is fixedly connected to the corresponding retractable part, and the other rebar head clamp seat is slidably connected with the corresponding retractable part through a linear slide. The device according to the scheme has the advantages that in cutting, the rebar head clamp seats can clamp a spiral rebar, the spiral rebar is cut off from between the two rebar head clamp seats, and cutting stability is guaranteed; after cutting, the rebar head clamp seats slidably connected with the retractable parts slide linearly, the stirrup ends clamped by the rebar head clamp seats move axially along with the rebar head clamp seats and are aligned with the other ends, and subsequent normal welding is guaranteed accordingly.