The invention discloses sintered flux for 9Ni steel welding, and relates to the technical field of welding materials. The sintered flux comprises the following components in parts by weight: 20 to 28 parts of CaF2, 23 to 33 parts of MgO, 15 to 18 parts of Al2O3, 8 to 12 parts of CaO, 4 to 10 parts of SiO2, 0.5 to 2 parts of BaO, 0.5 to 2 parts of TiO, 0.5 to 2 parts of ZrO2, 0.5 to 2 parts of alloy and 15 to 20 parts of water glass, wherein the alloy is ferrosilicon or manganese-silicon or a combination of ferrosilicon and manganese-silicon. The preparation method comprises the steps of uniformly mixing the components according to the proportion; carrying out granulation; drying at the low temperature of 300 to 400 DEG C; and sintering at the high temperature of 660 to 750 DEG C, so as to obtain a flux finished product. According to the sintered flux, the flux is matched with a solid welding wire ERNiCrMo-4, the welding manufacturability is relatively good, the mechanical property of weld joints is good, the ultra-low temperature toughness of deposited metals is stable and excellent, the hot crack resistance sensitivity is good, and the sintered flux is applicable to submerged arc flat welding and horizontal welding of 9Ni steel.