The invention relates to a treatment method of oily sludge, which is particularly suitable for oily sludge generated during the sewage treatment process of a refinery plant. The method comprises the following steps: after centrifugal dewatering, the oily sludge is dehydrated through rotary dehydration equipment under the control of a certain negative pressure and a certain temperature, so as to destroy the water, oil and solid stable system in the oily sludge; parts of oil and water in the oily sludge are distilled out; the coke generated after dehydration is extracted with a solvent; after extraction, the material undergoes the solid-liquid separation; the separated liquid phase is delivered to a delayed coking device; the separated solid phase is dehydrated to form the residues that meet the discharge standards for solids; and the wastewater generated during the process is biochemically treated and then discharged after reaching the discharge standards. The invention is mainly characterized in that the sludge treatment process is short, the speeds and the efficiencies of sludge dehydration and extraction are high, the effect is good, the operational condition is moderate, the energy consumption is reduced, the oily sludge treatment effect is good, and the operating maintenance of the equipment is simple.