Extraction residue of coal liquefaction residue (ER) refers to the substance remaining after obtaining heavy oil and asphaltthrough extraction from coal direct liquefaction residue, accounting for about 15% of the original coal amount. By using scanning electron microscopy (SEM) to observe the loose and porous structure on the surface of the ER, the ash content can be reduced by flotation,and it can be used to produce activated carbon. Due to the adhesion of heavy oil and asphalt to the surface of unreacted coal in the extract,various substances in the ER have indistinguishable hydrophobicity, making flotation difficult. Therefore, heat treatment was used to remove heavy oil and asphalt, reducing the overall hydrophobicity of the ER and increasing the difference between unreacted coal with hydrophobicity and hydrophilic silicate minerals and catalysts (Fe7S8). After heat treatment to remove heavy oil and asphalt, the remainingsilicate minerals and catalysts remain hydrophilic and remain in the pores and surface of unreacted coal. Therefore, ultrasonic treatmentwas used to remove these hydrophilic substances, exposing the hydrophobic surface of unreacted coal. At this time, the hydrophobicity ofthe ER increases, and the difference between coal and hydrophilic impurities increases, which is beneficial for flotation. Flotation testswere conducted on the EER before and after treatment. The results shows that it is difficult to perform flotation on the original sample of theER. The ER after calcination at 260 ℃ for 1 hour in a muffle furnace can be subjected to flotation. On the basis of heat treatment, ultrasonic treatment was carried out. With the increase of ultrasonic treatment time, the clean coal yield shows an upward trend and theash content shows a downward trend. The flotation clean coal yield and ash content of the ER treated with ultrasound for 10 minutes are58.20% and 23.63%, respectively. Compared with the ER treated only with heat, the flotation clean coal yield increases by 17.80% andthe ash content decreases by 2.88%. Both heat treatment and ultrasonic treatment have a promoting effect on flotation. Scanning electron microscopy and DSA100 contact angle analyzer were used to detect and analyze the surface characteristics of the ER before and afterultrasonic treatment. Through scanning electron microscopy, it is observed that there are a large number of impurities adhered to the surface of the ER. As the ultrasonic treatment time increases, the surface impurities gradually decreases, the contact angle gradually increases, and the hydrophobicity increases. Scanning electron microscopy and contact angle analysis both support the flotation results.