Abstract: In this paper, the circular piston high-frequency transducer with low side-lobes is studied. The low side-lobe is realized by the non-uniform ring-removal method for the circular piston transducer and the corresponding directivity expression is derived. The directivity simulation model of non-uniform ring-removed circular piston transducer is established and optimized with Matlab. The variation of side-lobes with ring-removed position and width on the circular piston transducer is analyzed, and the bandwidth is expanded by adding matching layer. The low side-lobe broadband circular piston high-frequency transducer is prepared and measured, and the measurement results are basically in agreement with the simulation results. The measured maximum side-lobe of the transducer is -22.4 dB, which is 4.8 dB lower than that of the uniform piston array. The measured center frequency of the transducer is 325 kHz, and the -3 dB bandwidth is 150 kHz.