The invention relates to the technical field of soil improvement, in particular to a saline alkali soil conditioner and a use method. The saline alkali soil conditioner is prepared from raw materialsin parts by weight as follows: 3-10 parts of desulfurized gypsum of a power plant, 2-10 parts of blast furnace slag, 80-95 parts of vinegar residues and 3-10 parts of a citric acid solution with content of citric acid being 1% in percentage by mass, and during using, the saline alkali soil conditioner is uniformly scattered on the surface of saline alkali soil in certain sequence and mixed uniformly with soil. According to the saline alkali soil conditioner, the vinegar residues and the citric acid solution are particularly added and matched with each other, so that pH value of soil can be reduced within shorter time, and the effect of improving soil fertility is realized; the blast furnace slag is rich in medium trace elements such as silicon, calcium, magnesium and the like required forplant growth, and functions of improving plant adverse resistance and promoting growth of plants are achieved; the product is prepared from solid waste as a main raw material and has positive significance for resource regeneration and environmental protection, meanwhile, the raw materials are easily available, the preparation process is simple, and the technology is controllable.