Movable cast-in-situ support and movable construction method of box girder cast-in-situ support

The invention discloses a movable cast-in-situ support, comprising buttresses, distribution girders, gliding systems, longitudinal girders, templates, traction devices and lifting devices, wherein the buttresses at least comprise two side buttresses; the distribution girders are fixed on the buttresses; the gliding systems are installed on the distribution girders, and each gliding system comprises a lateral gliding system and a longitudinal gliding system; the longitudinal girders are installed on the gliding systems; each template comprises a bottom template and two side templates and is bolted on the longitudinal girders; the traction devices drag the longitudinal girders and the templates to glide on the distribution girders; and the lifting devices are installed below the distribution girders. During construction, firstly a first-hole box girder is poured, and then the templates are separated to separate the templates and the girder box; the traction devices are started; the longitudinal girders and the templates are dragged to the next appointed position; and after the templates are assembled, the next-hole box girder is poured. The method has the advantages of low cost and strong bridging capability, lowers labor intensity on splicing, can be used for constructing in narrow areas, and serves as a supplementary cast-in-situ support form between a landing support and a movable formwork bridge fabrication machine.