Abstract: The degradation of the Rhodamine B and the sewage is investigated based on the hydrodynamic cavitation in this paper, including the factors affecting the degradation, such as the cavatation number, the sewage initial concentration, and the cyclic and inlet pressures. It is shown that the degradation of the pollutant water increases with the increase of the inlet pressure, the best degradation of the Rhodamine B occurs in the range of 4 mg/L~10 mg/L, and the TP (total phosphorus) degradation is better than NH4+ by zoo percent.