The invention belongs to the technical field of ore processing, and relates to a method for determining the pre-separation reasonable coarse-size separation grade of oxidized refractory iron ore. Themethod comprises the steps that 20 kg of oxidized refractory iron ore with the particle size being 0-15 mm is sampled before pre-separation, the sample is evenly mixed and reduced to a 1 kg sample, the 1 kg sample is added with steam coal with the mass being 2-4% that of the sample so that the mixture can serve as a reduction agent and be evenly mixed, magnetizing roasting is conducted through a muffle furnace at the temperature of 650-750 DEG C for 20-30 min, the iron ore subjected to magnetizing roasting becomes strongly-magnetic ore from weakly-magnetic ore and is naturally cooled to the room temperature, after the iron ore subjected to magnetizing roasting is scattered, manual dry pre-separation is conducted through 1200-1800 Oe field strongly-magnetic blocks, surrounding rocks are separated from the ore, reduction sampling is conducted on the surrounding rocks and the ore, the content of iron in the surrounding rocks and the ore is detected, and the content of iron in the surrounding rocks is the reasonable pre-separation coarse-size separation tailing grade, namely the authentic surrounding rock iron content. According to the method, the problems that the pre-separation coarse-size separation grade of the oxidized refractory iron ore cannot be determined accurately, thus, resources are wasted, or waste rocks are discharged along with the ore, and the cost of roasting andgrinding separation in the later period is increased are solved.