The change in material microstructure caused by ferroelectric domain switching under an alternative mechanical and electrical field is considered to be a major cause for degradation and failure of ferroelectric materials. It is shown that Raman spectroscopy could be used as a nondestructive, micro-regional and sensitive technique for in-situ observations of domain switching and microstructure changes for polycrystalline ceramics with home-made experimental apparatuses. The lanthanum-doped lead zirconate titanate (PLZT) ceramics with atomic ratio Zr/Ti=53/47 were prepared with conventional solid state reaction technique. The crystal phase and morphology of the PLZT specimen were characterized with XRD and SEM techniques, with the ferroelectric physical properties with Precision_LC system. The compressive stress was applied to the PLZT specimen and in-situ Raman measurements were carried out through the self made microtest mechanical loading device. The effects of stresses and polarization directions of the scattered light on the Raman spectra intensity and peak position for E(2TO) and E(3TO+2LO)+B1 soft modes were discussed and analyzed. The results revealed that both variations of peak intensity with the polarization degree for E(2TO) and E(3TO+2LO)+B1 soft modes showed an periodicity in a sine type law, which increased to the highest value at 60° and decreased to the lowest value at 150°. With the increase of the compressive stress, the peak intensity for E(2TO) and E(3TO+2LO)+B1 soft modes showed a significant decrease at the polarization degree of 0° and 60°, whiel it remained unchanged at 90° and 150°. The compressive stress has no effects on the peak position for E(2TO) and E(3TO+2LO)+B1 soft modes.