The invention belongs to the technical field of welding materials, and relates to a self-shielded flux-cored wire used for downward welding and horizontal position welding. A flux core of the self-shielded flux-cored wire is prepared from, by weight, 8-10% of manganese, 2-5% of chrome, 0.2-2% of zirconium, 3-8% of aluminum, 5-9% of carbonate, 11-20% of calcium fluoride, 7-10% of calcium oxide, 3-13% of zirconium oxide, 0.5-3% of ferric oxide and the balance iron powder. The manufactured self-shielded flux-cored wire has good plasticity and strength, splatter is little and is fine particle splatter, the welding performance of downward welding and horizontal position welding is excellent, slag detachability and weld seam formability are obviously improved, the content of the S element of deposited metal is very low, and excellent hot-crack-resisting performance is achieved. The self-shielded flux-cored wire is suitable for welding medium and thick steel plates at the same strength level, particularly suitable for welding butt-joint welding seams of a deep groove steel plate and capable of being widely applied to machine manufacturing, building and welding of structural parts with the low requirement for impact toughness.