Abstract: The ultrafast carrier dynamics and terahertz conductivity of cadmium telluride (CdTe) are investigated by optical-pump terahertz-probe spectroscopy at room temperature. The amplitude of the photoinduced absorption of CdTe increased gradually with the pump fluence under the femtosecond pumping excitation at 800 nm. The carrier-relaxation process was fitted with a single exponential function. The carrier relaxation process of CdTe takes several nanoseconds and decreases with the increase of pump energy density, which is related to the trapping of electrons by deep-level defects; the defect trapping prolongs the radiation recombination time. With the increase in the pumping optical density, part of the trap is filled, resulting in a decrease in the radiation recombination time. The Drude–Smith model was used to fit the transient composite photoconductivity of CdTe. With the increase in pump fluence, the Smith parameter c₁ decreased from -0.7 to -0.95, and the scattering time τ_S increased from 155 fs to 205 fs, indicating that the internal carrier dynamics of CdTe is localized rather than freely scattered. The localization degree increased with pump fluence, which is related to the localization of CdTe deep-level defects on electrons. This study provides important data support and a theoretical basis for the design and fabrication of high-speed optoelectronic devices of CdTe.