Abstract: Catalytic clarification oil can be blended in the delayed coking device with small proportion to solve the problem of oil slurry outlet. The experimental results of Dushanzi petrochemical 1.2 Mt/a delayed coking device showed that: ① it had minor effect of small proportion of blending catalytic oil slurry on heat exchange of the coking unit; ② the yield of wax oil and coke slightly increased, dry gas and the liquid yield slightly decreased; ③ it had no effect on coke quality and process operation; ④ the coking trend of heating furnace tube didn't increase after blending, and it also didn't cause the damage of equipment; ⑤ the economic benefit reached 1 328×10⁴ RMB yuan per year after blending catalytic oil slurry, which showed it was feasible for blending catalytic oil slurry with small proportion.