In this work, the effect of ultrasonic pretreatment time on oxidized coal flotation was studied. Analytical techniques, such as particle size distribution (PSD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle measurement, and specific surface area/pore analysis, were used to examine the changes in the physicochemical characteristics of the coal samples before and after ultrasonic pretreatment. The results showed that the flotation kinetics and yield of the clean coal initially increased with ultrasonic pretreatment time. The maximum clean coal yield (79.6%) and maximum value of the flotation kinetics constant were obtained within 10 min of ultrasonic pretreatment. The hydrophilic oxidized layer on the coal surface was effectively removed by ultrasonic cavitation, as identified by PSD, SEM, XPS, and contact angle, which increased the flotability and recovery of oxidized coal. However, prolonged ultrasonic pretreatment proved detrimental to oxidized coal flotation. The fresh exposed surface was reoxidized by the hydroxyl free radicals produced during the cavitation process. It is expected that the results of this work will provide guidance in ultrasonic flotation for oxidized coal.