The invention discloses a low-pressure mold-filling high-pressure solidification casting device and a casting method, which can be used in an anti-gravity casting machine or an extrusion casting machine. The device comprises a casting mold, a metal melt lifting channel and a shunting cone, wherein a mold cavity is formed in the casting mold, the shunting cone can move up and down, and the shuntingcone has the effects of shunting and guiding metal melt at a liquid lifting stage and pressing a filter screen, so that a mold is stably filled with the metal melt in a mode of laminar flow. After the mold is filled, the shunting cone moves downwards to press a sprue bushing so as to form a sealing structure, and a metal melt inlet of the sprue bushing and the mold cavity is sealed. Then high pressure charging is performed on the metal melt, so that the metal melt is solidified at high pressure, the pressure range can reach 0.1 MPa to 160 MPa, and the defects of shrinkage cavities, shrinkageporosity, inclusions, slag inclusions and the like are avoided. Additionally, optimum structural design is performed on the shunting cone, so that low-pressure controllable stable mold filling and high-pressure solidification forming of the metal melt are guaranteed. While the metal melt in the mold cavity is applied by a pressure mechanism, the metal melt in the metal melt lifting channel cannotform a solidification shell, so that the service life of equipment is prolonged.