The invention discloses a high-temperature sandstone reservoir retarded acid which is prepared from the following raw materials in parts by weight: 5-15 parts of hydrochloric acid, 10-25 parts of lactate ester compounds, 0.5-5 parts of citric acid, 2-8 parts of ammonium hydrogen fluoride, 2-5 parts of a high-temperature corrosion inhibitor, 0.5-2 parts of a surfactant and 40-80 parts of water. Slow hydrolysis reaction can be carried out on the lactate ester compounds at higher temperatures to generate lactic acid which is not only a good retarded acid, but also is a chelating agent. Meanwhile, calcium salt and magnesium salt of the retarded acid are relatively high in solubility, so that the retarded acid disclosed by the invention not only can satisfy the requirement on deep substrate acidification of a high-temperature stratum, but also can be used for overcoming the defect that when formic acid and acetic acid are increased, precipitates of calcium salt and magnesium salt are easily generated to block the stratum, thereby reducing the corrosion to a tubular column of an oil well, alleviating the damage to the stratum, slowing down the reaction speed and enhancing the substrate acidification effect of the deep stratum.