The invention provides a flux-cored wire used for low-alloy chrome molybdenum heat-resistant steel. The flux-cored wire comprises a low-carbon steel sheath and a flux core which is stuffed in the low-carbon steel sheath. The flux core comprises the following components in percentage by mass: 30-35% of natural rutile, 2-5% of magnesium oxide, 1.5-3% of barium carbonate, 2-3% of elpasolite, 2-5% of potassium titanate, 15-20% of a silicomanganese alloy, 8-10% of chromium, 3.5-5% of ferromolybdenum, 1-2% of ferro-aluminum, 0.5-2.5% of roasted aluminum oxide, 0.5-1% of nickel powder, 0.5-1.5% of magnetite and the balance of iron powder and inevitable impurities. The flux-cored wire has the advantages that deposited metal composition completely accords with stipulation of related national standards, and the all-position welding requirement of the 1-1.25%Cr-0.5%Mo heat-resistant steel can be met; meanwhile, the mechanical performance indexes of deposited metal completely accord with stipulation of related national standards; impact property of the deposited metal is excellent, and specially, low-temperature impact toughness (minus 30 DEG C) is stabilized at more than 50J; and an impact value is stable.