The treatment of electric desalting wastewater with a high oil content and strong emulsification is one of the most difficult problems in refineries. An industrial pilot study was carried out using swirling flotation coupled with medium coalescence. The self-adaptive structure was designed for swirling flotation and the coalescence medium was a combination of fibers and granules. The effects of the flow rate, gas injection mode, gas flow rate, and the depth of the medium bed on the separation performance were investigated. Under optimum operating conditions, when the inlet oil content is 400–2500 mg/L, the oil removal efficiency of the swirling flotation is 90% and the total oil removal efficiency is up to 98.63%. The oil content, suspended solids content, and chemical oxygen demand (COD) of the effluent can be stabilized below 30 mg/L, 15 mg/L, and 700 mg/L, respectively, which meets the requirements for discharge to a downstream treatment plant. This study provides a new technical idea for the treatment of electric desalting wastewater with the advantages of a high operation elasticity, a rapid treatment process, and a high efficiency. Display omitted •The characteristics of EDW in refineries were comprehensively investigated.•A technique of using swirling flotation coupled with medium coalescence was proposed.•The optimal operating parameters for the technique were optimized by an industrial pilot.•The study provides a new technical concept for treatment of EDW with high efficiency.