To explore the effect of Terahertz(THz) on neurogenesis in the Subgranular Zone(SGZ) of the hippocampal dentate gyrus of adult mouse and the cognitive ability of elderly mouse, the heads of mice in THz group are irradiated with THz radiation for 10 min/time, 2 times/d, for 21 days. The mice in the control group are anesthetized for the same time. 5-Bromodeoxyuridine(BrdU) staining is utilized to evaluate the survival of newborn cells. BrdU/Neuron nucleus(NeuN) staining is adopted to evaluate cell differentiation. The Morris Water Maze(MWM) experiment is employed to analyze the changes in cognitive ability. Results indicate that 0.14 THz radiation for 10 min/time, twice/d, for 21 days can effectively promote SGZ neurogenesis in adult mouse without affecting the differentiation of newborn cells into neurons compared with the control group, and the survival of SGZ newborn cells in adult mouse is significantly improved(P<0.05), while the differentiation of newborn cells into neurons is not significantly changed. There are no significant changes in the escape latency and the locus of movement in the elderly mouse. It is concluded that THz irradiation does not affect the spatial cognitive ability of old mouse.