The invention discloses a treatment method of inertia chlorination waste slag. The method comprises the following process steps: (S1) the inertia chlorination waste slag is aired to reach the water content of less than 6%; (S2) the content of petroleum cokes in the aired inertia chlorination waste slag is detected; (S3) ilmenite is mixed; when the content of the petroleum cokes in the aired waste slag is within 50-60%, the mixing mass ratio of the waste slag to the ilmenite is 1: 2-1: 3; and when the content of the petroleum cokes in the aired waste slag is within 60-80%, the mixing mass ratio of the waste slag to the ilmenite is 1: 3-1: 4; (S4) mixed raw materials are added in a rotary kiln for calcining from the tail of the rotary kiln; coal powder is sprayed in at the head of the kiln by a coal spraying gun; and the ratio of the coal powder to the ilmenite is 1: 13-1: 15; (S5) the calcined product is transferred into a cooling kiln for cooling, and is discharged from the kiln when cooling to reach a temperature of 25-30 DEG C; and (S6) reduction titanium is obtained through magnetic separation. The treatment method directly applies the aired inertia chlorination waste slag to production of the reduction titanium, has no need to add related equipment for treating solid wastes, is convenient for operation and high in feasibility, and satisfies three rules of reduction, harmlessness and resourcefulness in waste treatment to the greatest extent.