This paper presents the use of hydrodynamic cavitation and ultrasonic cavitation technologies for treating rhodamine B (RhB) in simulated wastewater. Various parameters of each technology that influence the RhB degradation rate were compared and optimized. The results showed that the optimal conditions for the hydrodynamic cavitation determined by the single-factor method were as follows: inlet pressure, 0.4 MPa; initial concentration, 10 mg L⁻¹; reaction temperature, 30 °C; and pH value, 3. The RhB degradation rate was 38.7%. In addition, the optimal conditions for the ultrasonic cavitation determined by the response surface methodology were as follows: initial RhB concentration, 10 mg L⁻¹; ultrasonic power, 850 W; ultrasonic time, 100 min; addition amount of H₂O₂, 0.6%; and pH value, 3. The RhB degradation rate was 84.06%. We also found that the degradation of RhB by both cavitation technologies conformed to the first-order kinetic reaction model. The rate constant of UC was 5.22 × 10⁻³ min⁻¹ and that of HC was 4.35 × 10⁻³ min⁻¹. The ultrasonic cavitation has a stronger cavitation effect than hydrodynamic cavitation.