The invention relates to a treatment process of high-slag-content and water-containing sump oil and relates to the technical field of separation and treatment of slag-containing and water-containing sump oil. Firstly, the sump oil is washed with alkali liquor, emulsification systems of a W/O type and an O/W/O type in the sump oil are subjected to phase inversion to form emulsion of an O/W type, the viscosity of the high-slag-content and water-containing sump oil and the interfacial tension of the emulsion systems can be effectively reduced due to formation of the emulsion of the O/W type, and therefore mass transfer of a subsequent demulsifying agent is facilitated, and the demulsifying effect of the subsequent demulsifying agent fully acts. Then, sulfuric acid is added and made to react with sodium naphthenate, sodium naphthenate is reduced into naphthenic acid without the emulsifying effect, and therefore the emulsifying effect of sodium naphthenate is eliminated. Next, a demulsifying agent of a compound type and a flocculating agent are sequentially added, and further flocculating setting separation happens to part of dross remaining in an oil layer. Finally, the sump oil is treated through the acoustic cavitation effect of ultrasonic waves, the mechanical vibration effect and the heat treatment effect, water and slag are further removed, and crude oil is recycled.