A theorem on Butterworth matching for piezoelectric ceramic emission transducer is presented and proved.The complicated problem of broad-band matching is changed to a simple arithmetical one due to explicit formulas of the theorem.It is shown in an example that after matching,bandwidth of the transducer increases remarkably while the power gain is close to 1. A theorem on Butterworth matching for piezoelectric ceramic emission transducer is presented and proved. The complicated problem of broad-band matching is changed to a simple arithmetical one due to explicit formulas of the theorem. It is shown in an example that after matching, bandwidth of the transducer increases remarkably while the power gain is close to 1