Abstract: Lanthanum-doped lead zirconate titanate (PLZT) ceramics were prepared by conventional solid state reaction technique and polarized in different directions. Then the cyclic loading fatigue experiment under an alternating electric field was conducted on the ceramics. The Raman spectra and hysteresis loops were in-situ measured at different cycles, and then the variations of Raman spectra intensity for soft modes and remanent polarization were analyzed. The results show that Raman spectra intensity and ferroelectricity of the ceramics decreased due to the domain switching produced during the fatigue process under the cyclic alternating electric field. With the increase of the cycles, the Raman relative intensity for soft modes and the relative intensity for remanent polarizationin decreased first rapidly then slowly with the same turning point at about 10^6.2 cycles. The Raman relative intensity for soft modes and the relative intensity for remanent polarizationin of the out-of-plane polarized specimen decreased with the largest reduction among those of non-polarized and in-plane polarized specimens, with the cycle increasing.