The invention discloses a solid-phase oxidation modification method for converter steel slag. The method comprises the following steps: weighing 50g of raw steel slag and loosely filling a remaking alumina crucible with a volume of 100mL with the raw steel slag; placing the remaking alumina crucible in a high-temperature box-type muffle furnace; charging N2 into the furnace to guarantee no air existing in the muffle furnace at first before an experiment; setting a heating speed to be 10 DEG C/min; when a temperature reaches 1100 DEG C, replacing N2 with synthetic air; monitoring the charging amount of the synthetic air through an LZB glass rotameter; adjusting the charging amount of air to be 7.5L/min; and after a set oxidation time reaches 40min, replacing the synthetic air with the N2 and rapidly cooling to reach room temperature. According to the method, fine steel slag powder with a particle size of less than 0.3mm is taken as a main research target; a manner of calcining in an oxidizing atmosphere is adopted for completing the transformation of aggregation of non-magnetic ferrous oxide and magnesium oxide in raw steel slag ores towards a magnetic iron rich phase; and an oxidation modification result is evaluated through magnetic separation.