Characteristics of dynamic hydrocyclones are introduced. The advantages of dynamic hydrocyclones, such as wider applicable flowrate range, smaller cut size, etc., are analyzed compared with normally used static hydrocyclones. By analyzing the inside velocity field distributions, the reason why dynamic hydrocyclones have higher efficiency than static ones is further described. Laboratory experiments and field tests of dynamic hydrocyclones were carried out. Relationships of flowrate, outer shell rotation speed, and split ratio with pressure were studied. Pressure and pressure drop inside hydrocyclones were measured and analyzed. The effect of main operating parameters, such as split ratio and rotation speed, on hydrocyclonic separation performance was also studied. It is shown that the rise of split ratio is beneficial for enhancing the separation efficiency, but the split ratio must be controlled in an appropriate range so as to obtain satisfactory separation results. The increase of rotation speed is helpful for the forming of an oil core inside the dynamic hydrocyclone, but the vibration phenomenon should also be avoided. Field tests, as anticipated, indicated satisfactory results. [DOI: 10.1115/1.4002997]