To address the challenge posed by the highly stable oil-water-solid emulsified structure formed by the intimate mixing of oil, water, and solid particles in drilling sludge, which makes oil-water separation and oil removal difficult, the high oil-content drilling sludge was employed as the research object. A synergistic thermo-chemical washing process was developed using sodium dodecyl benzene sulfonate (SDBS) as the surfactant, assisted by Na2CO3 solution and ethanol. By systematically optimizing key parameters, including the liquid-to-solid ratio, stirring time, heating temperature, and surfactant concentration, the optimal oil removal conditions were determined. The results revealed that, under the conditions of a liquid-to-solid ratio of 3∶1, a stirring time of 60 min, heating temperature of 70 ℃, and 0.8% SDBS, the residual oil content of the sludge decreased from 11.3% to 1.7%. After treatment, the appearance of the oily sludge transformed from a dark brown viscous mass to a loose brown powder or fine granules. The average particle size decreased from 4.8 μm to 1.3 μm, the water contact angle decreased from 109° to 85°, the Zeta potential increased from -41.3 mV to -22.5 mV, and the biological toxicity dropped to only 29.8% of that of the untreated sludge. These findings demonstrate that the SDBS-assisted thermo-chemical washing process effectively disrupts the oil film structure, reduces the stability and interfacial tension of the emulsified system, and modifies the surface charge distribution of the particles, thereby weakening their adsorption and aggregation. As a result, the oil removal efficiency is significantly enhanced, and the biological toxicity is substantially reduced. This method provides both theoretical and technical support for the demulsification and oil-phase removal of oil-water-solid emulsified systems in drilling oily sludge and related washing wastewater.