The invention discloses a stirring device for preparing a metal-based composite material. The device comprises a stirring container, a stirring shaft and a stirring blade, wherein the stirring container is provided with a cavity for melt storage; the cavity comprises a bottom section with a lower arc surface and a medium section which is tangent to the top of the bottom section and has gradually reduced diameter; the stirring blade comprises a first face, a second face and a third face, the first face and the second face are parallel to the axes, the third face is respectively obliquely crossed with the first face and the second face, the first face and the second face are crossed at the first side edge; the first face comprises a second side edge positioned at the bottom of the first face; two ends of the crossed line of the third and first faces are respectively positioned on the first side edge and the second side edge; and the included angle between the crossed line of the third and second faces and the first side edge is 30-60 degrees. According to the method, the melt can generate enough axial flowing, the staying area above the stirring blade and the staying area under the stirring blade can be reduced, and uniform stirring of the blade can be ensured.