The invention discloses a device and a method of light production of a carbon microsphere by using residual oil/coal tar, and belongs to the field of oil refining, petrochemical industry and coal chemical industry. The method organically combines technologies of hydrotreatment, rectification, polymerization reaction and centrifugal separation and comprises the steps of separating the residual oil/coal tar via a rectification tower after hydrotreatment, producing gasoline on the top of the tower, producing light diesel oil and heavy diesel oil in the middle of the tower, performing the polymerization reaction, the centrifugal separation, solvent mixing and water washing on a product at the bottom of the tower to produce the carbon microsphere urgently needed by China, and obtaining a byproduct impregnant pitch at the same time. The device and the method can remove most impurities such as sulfur, nitrogen and heavy metals in a raw material; at the same time, macromolecular polycyclic aromatics can be saturated into tricyclic aromatics or tetracyclic aromatics; the performance of the raw material is significantly improved; operating conditions are optimized; a light oil yield is increased; the obtained gasoline, the light diesel oil and the heavy diesel oil are product oil; heavy oil at the bottom of the tower is a high quality raw material for the polymerization reaction; in addition, the carbon microsphere with a high added value is generated; the industrial application yields good economic returns; and the industrial device is short in investment recovery period.