Piezoelectric catalysis is the catalytic action driven by the force-electrical conversion of piezoelectric materials. In this paper, the piezoelectric activity of K_0.5Na_0.5NbO₃ (KNN) was thoroughly investigated by annealing KNN at a series of temperatures and poling KNN under different electric-fields. With the application of an ultrasonification, the degradation activity for the Rhodamine B (RhB) dye molecules of the poled KNN was 253% higher than that of unpoled samples. The piezocatalytic activity of the poled KNN was significantly improved, which stemmed from the orderly ferroelectric domain to effectively reduce the recombination rate of the carriers by the built-in electric field. In addition, the superior piezocatalytic activity was achieved at KNN materials with the average grain size of ~0.29 μm, and after 160 min of mechanical vibration, the degradation rate of RhB (~5 mg/L) was as high as 95.7%. The high mechanical catalytic degradation rate of KNN materials reveals a bright application prospects in vibration catalytic degradation of organic pollutants.