Abstract: Combining the advantages of ultrasonic cleaning and properties of supercritical carbon dioxide, an experimental platform of ultrasound enhanced supercritical CO₂ composite cleaning is designed. The maximum acoustic power of ultrasonic transducer is 1200 W, and in a working cycle of 30 s the transducer works for 10 s and keeps silent for 20 s. The descaling experiment of CD03 steel sheet is carried out on the experimental platform. SEM and EDS analysis are performed on the surface of CD03 steel sheet by using ZEISS Merlin high resolution thermal field emission scanning electron microscopy. The experimental results show that with the prolongation of cleaning time, the rust gradually peels under the action of ultrasound. After the appropriate number of working cycles of ultrasonic action, the cleaning effect reaches the best. If the ultrasonic action time is too long, the substrate will be damaged. The oil removal experiment for the surface of carbon steel sheet is also carried out on the experimental platform. Leica optical microscope is used to observe the surface of the cleaned carbon steel sheet. The cleaning effect is calculated and analyzed by JA2003 electronic scales method. In the same way, there is an optimal cleaning time for ultrasonic-supercritical carbon dioxide oil cleaning. However, the optimal cleaning time for different pollution is different or even varies greatly. In actual cleaning, the optimal cleaning time should be determined according to the type of pollutant and then cleaned.