In this study, high quality 0.3BaSrTiO₃-0.7NdAlO₃ microwave dielectric ceramics are prepared using solid state reaction method. Their absorption characteristics in the terahertz range are investigated using terahertz time-domain spectroscopy. It is observed that the absorption coefficient could be modulated using the external optical pump at the 18 ℃(291 K), and the tunability could reach up to 34.46% at 0.55 THz. By fitting the dielectric constant and light power of 0.3BaSrTiO₃-0.7NdAlO₃ ceramics at 0.45 THz and 0.55 THz, the anharmonic parameter α are observed to be 1.273×10 ^-8 and 1.823×10 ^-8, respectively. In addition, the micro-mechanism of absorption coefficient modulation with the intensity of external light pump is attributed to the internal space charge field in the 0.3BaSrTiO₃-0.7NdAlO₃ ceramics caused by the excited free carriers.