The invention provides a method for preparing barium carbonate and potassium chloride by using barium chloride waste residue, which comprises: fully dissolving barium chloride waste residue from the preparation of thiourea by reaction of hydrochloric acid and barium sulfide in water, and mixing the solution with hydrochloric acid for reaction to obtain solution containing barium chloride; mixing the solution containing barium chloride with potassium carbonate for reaction to obtain barium carbonate and potassium chloride; filtering to obtain a barium carbonate filter cake and solution containing potassium chloride; washing, crushing and drying the barium carbonate filter cake to obtain a barium carbonate product; and distilling the solution containing potassium chloride to obtain oversaturated solution of potassium chloride, crystallizing and precipitating potassium chloride to obtain a potassium chloride product. In the method, operation is simple, equipment investment is small, and active ingredients in barium chloride waste residue are converted into materials that can be used in industry. Thus, the method is economic and applicable.