The invention discloses a method for preparing a nickel-cobalt-manganese ternary material precursor by using a nickel-cobalt slag material. The method comprises the following steps: step (1), carrying out acid leaching treatment on the nickel-cobalt slag material with the nickel-cobalt mole ratio of 3/1 to 8/1 at the pH of 1 to 5 and the temperature of 30 to 80 DEG C, and then carrying out solid-liquid separation to obtain an acid leaching slag material with the nickel-cobalt mole ratio of 1: (0.9 to 1.1); step (2), carrying out hydrogen peroxide reduction leaching, chemical subtraction and extraction purification on the acid leaching slag material to obtain a nickel-cobalt solution; and step (3), adding manganese sulfate into the nickel-cobalt solution, and carrying out coprecipitation to obtain the nickel-cobalt-manganese ternary material precursor. In the method, the nickel-cobalt slag material is leached under the synergism of pH and temperature, the acid leaching slag material with the mole ratio of close to 1: 1 is obtained, then the reduction leaching, subtraction, purification and coprecipitation are carried out, and then the nickel-cobalt-manganese ternary material precursor meeting the requirement is obtained in one step.