Nanocomposite scintillators are expected to combine the advantages of inorganic and plastic scintillators, such as high detection efficiency, high light yield, fast decay time, low cost, and ease of processing. They are currently the forefront and hot field of scintillator research. In this study, a non-destructive method was developed for measuring the content of inorganic components in nanocomposite scintillators by terahertz time-domain spectroscopy. The complex refractive index of B a F 2 nanocomposite scintillators with different mass contents was measured in the terahertz band. As the mass content of B a F 2 nanoparticles increases, the refractive index and extinction coefficient of B a F 2 nanocomposite scintillators also gradually increase in the terahertz band. By combining the effective medium theory, the expected mass content was obtained, proving the feasibility of this measuring method.