The invention discloses an oil removing pretreatment technology for petroleum oil refining wastewater. According to the oil removing pretreatment technology, a water collecting tank with gratings is used for separating sand and sludge; a three-phase cyclone liquid separation floating oil collecting and discharging adjusting tank is used for achieving separation of water, oil and residues; a cyclone oil coarse graining polymerization oil-water separator is used for removing fine oil grains; a dissolved air flotation device is used for demulsification and flocculation reaction, wherein air bubbles and suspended solids in wastewater make contact for adhesion and float upwards, and the standard is met through residue scraping. The technology is simple, the structure is scientific, the three-phase cyclone liquid separation floating oil collecting and discharging adjusting tank, the cyclone liquid coarse graining polymerization oil-water separator and the dissolved air flotation device jointly serve as the core treatment scheme, oily wastewater is pretreated through the density difference of oil and water based on the fluid dynamics principle, a physical method and a chemical method act jointly, and the oil content in the pretreated oily wastewater is smaller than or equal to 20 mg / L and reaches the standard. The oil removing pretreatment technology is large in daily treatment amount, high in oil removing efficiency, remarkable in oil collecting effect and considerable in economic benefit, and the water content of the recycled waste oil is 5% or lower.