The numerical simulation and experimental study on the non-destructive and destructive timber beams with piezoelectric ceramic (PZT) sensors are carried out based on the piezoelectric impedance technology, and the damage index, that is the root mean square deviation (RMSD), is used to quantitatively evaluate the relationship between the impedance value of the timber beams as a function of the damage degree and the damage location. The results indicated that the piezoelectric impedance method could efficiently estimate the local damage. The RMSD value increased with the increase of the damage degree when the distance between the PZT transducer and damage location was fixed, while the RMSD decreased with the increase of the distance between the PZT transducer and damage location when the damage degree was fixed. The numerical results are consistent with the existing experimental results. Both of the numerical results and the experimental results indicate that the piezoelectric impedance method can efficiently detect the local damage of the timber beams, which can provide a reference for engineering practice.