Terahertz time-domain spectroscopic technique was applied to investigate the spectral properties of (Pb, La)TiO3 (PLT) ferroelectric thin films prepared on SiO2/Si substrates. The terahertz spectra of three kinds of PLT thin films with different sintering temperatures were observed. According to the experimental data, the absorption coefficients, refraction indexes and dielecric constants of the PLT thin films were computed, and the experimental results of the three kinds of PLT thin films with different sintering temperatures in the effective frequency range were compared. The results indicated that the PLT thin films had strong absorption in the frequency range of measurement, and had an obvious absorption peak at 1.5 THz and a weaker absorption peak at 2.25 THz.