Based on the modified matrix pencil (MMP) method, an improved MMP (IMMP) method is presented. Compared to the MMP method, the IMMP method ensures the extrapolation accuracy and improves the computation efficiency by reducing one reduced-rank operation. By combining the IMMP method with the finite-difference time-domain (FDTD) method, fast analysis of the reverberation chamber can be realized.Index Terms-Finite-difference time domain (FDTD), matrix pencil method, reverberation chamber.