The invention provides a method for preparing nitrate and potassium sulfate mixed products from manganese-containing liquid waste, comprising the following steps of: carrying out pumping-filtration on magnesium-containing liquid waste obtained from hydroquinone production to obtain a clear filtrate containing manganese sulfate, ammonium sulfate and sulfuric acid and a filter cake containing elementary residue; reacting the filter cake containing elementary residue with an excess of sulfuric acid to obtain a solution containing calcium sulfate, magnesium sulfate, zinc sulfate, sodium sulfate, aluminum sulfate, cadmium sulfate and nickel sulfate; mixing with a potassium nitrate solution to undergo a reaction to obtain a nitrate and potassium sulfate mixed solution containing calcium nitrate, magnesium nitrate, zinc nitrate, sodium nitrate, aluminum nitrate, cadmium nitrate and nickel nitrate; filtering the mixed solution to obtain a calcium nitrate filter cake and a filtrate containing the nitrate and the potassium sulfate; and carrying out vacuum distillation and crystallization by cooling on the filtrate containing the nitrate and potassium sulfate to separate out a mixture of nitrate crystals and potassium sulfate crystals, filtering and separating the mixture to obtain the nitrate and potassium sulfate mixed products.