Sodium hydroxide and sulfuric acid，combined with demulsifier agent，was employed to treat the high solid content dirty oil with strong emulsification and stability. When the dosage of SP-3 demulsifier was 0.8 g/L，reaction temperature was 60℃ and reaction time was 120 min，the optimal addition amount of sodium hydroxide and sulfuric acid were achieved by orthogonal experiment，being of 40 g/L and 25 g/L，respectively，and after demulsification，the water content in oil layer could be decreased to 10.6%，realizing three-phase（oil，water and solid）separation. From the analytical data，including the content of oil，water and solid in oil layer，dirty oil component，surface tension and viscosity of oil layer，the effect of sodium hydroxide and sulfuric acid on dirty oil demulsification was investigated systematically. Therein，sodium hydroxide + sulfuric acid pretreatment could reduce the content of resin and asphaltene in dirty oil，destroy the net structure formed by solid，resin and asphaltene，make the solid particle separate from oil phase easily，and promote the coalescence of oil droplet and water droplet，respectively. Meanwhile，sodium hydroxide + sulfuric acid pretreatment could decrease the absolute value of Zeta potential obviously，thus lowering the intensity of interfacial film. Furthermore，sodium hydroxide + sulfuric acid + demulsifier could lower contact angle of water on the surface of solid particles in the dirty oil from 95.6° to 87.0°，enhancing the surface wettability of solid particle significantly. Sodium hydroxide + sulfuric acid pretreatment could decrease the viscosity，surface tension and stability of dirty oil. In general，the sodium hydroxide + sulfuric acid pretreatment combined with demulsifier agent can realize demulsification，dehydration and solid removal of the high solid content dirty oil effectively.