In this report, we have demonstrated a high degradation activity of MoSe2 nanoflowers with abundant single-layer and few-layer structure for decomposing the Rhodamine B (RhB) dye by the piezo-catalyst effect which is a technique for converting mechanical energy into chemical energy. Similar to photocatalyst effect, the electrons and holes also can be introduced by piezo-electronic effect. Base on our experiment results, the 10 ppm RhB solution was degraded by 90 % within 30 s through the application of the ultrasonic vibration. The significantly piezoelectric potential was evidenced by the piezoresponse force microscopy (PFM), and the tunneling atomic force microscopy (TUNA). The observed k_obs rate constant is 0.3 (ppm s−1) with a highly fast degradation rate of ~ 69,889 ppm L mole−1 s−1. Moreover, the electron paramagnetic resonance (EPR) spectroscopy also demonstrated the formation of the hydroxyl radical from the MoSe2 nanoflowers during the ultrasonic vibration in dark, which is the major reactive oxygen species (ROS) for destroying the dye molecules.