Choking cavitation is a recent technology of hydrodynamic cavitation. A swirling choking savitator can be formed by adding a swirling core into the nozzle of the choking cavitator. With different back pressures and swirling core lengths, a numerical simulation can be achieved of the internal flow field in the cyclone choking cavitator by using CFD software. The change of mass concentration of the phenol solution with different initial concentration can be treated with a high performance liquid chromatograph. The calculation results show that the vortex ring generated in the internal swirling choking cavitator helps to promote the choking cavitation, with an optimal back pressure and swirling core length. The simulation test results of wastewater treatment show that: when the pressure is 200 kPa, the swirling core length will be of 3/4 lead; when the initial concentration of phenol solution is 5 mg/L, an optimal phenol removal efficiency can be achieved by the swirling choking cavitator.