Abstract: With the development of Moore’s law, through-silicon via (TSV) has emerged as a critical technology for the realization of three-dimensional (3-D) integrated microsystem. TSV technology provides tremendous advantages, such as lower interconnect latency, higher chip integration density and fewer chip power consumption through the vertical stacking of multiple planar device layers. As a result, it profoundly satisfies the requisites of modern spacecraft for exceptional integration, miniaturisation, and multi-functionality in space operation. However, with the widespread application of 3-D integrated microsystem technology in spacecraft, there is little work available on the radiation reliability of TSV. In this paper, the total ionizing dose (TID) effect of customized TSV test chips was studied by using the irradiation of ⁶⁰Co γ-ray. The experimental results show that insertion loss (S₂₁) decreases and return loss (S₁₁) increases with the increase of cumulative dose, which demonstrates the deterioration of TSV signal integrity. Furthermore, there is a negative shift of C-V curve within TSV structure and the parasitic metal-oxide-semiconductor (MOS) capacitance within TSV structure decreases after γ-ray irradiation. It is proposed that γ-ray irradiation induced oxide trap charges and interface trap charges in the oxide layer, which leads to an increase in the total amount of oxide charges. Consequently, the flat-band voltage of parasitic MOS capacitance decreases and the state of parasitic MOS capacitance is transited from partial depletion to the full depletion after irradiation. This is the reason why the C-V behavior of parasitic MOS capacitance changes under ⁶⁰Co γ-ray irradiation. Furthermore, the decrease of parasitic MOS capacitance within TSV structure results in the variation of characteristic impedance of TSV signal channel. According to the transmission line characteristic in microwave networks, when the characteristic impedance on the transmission path is certain, the signal is not reflected. However, if the characteristic impedance of signal transmission channel becomes discontinuous, the reduction of effective output signal occurs and the reflection of signal increases. This illustrates the downward trend of S₂₁ curves and the upward trend of S₁₁ curves after irradiation. Furthermore, the discontinuity of characteristic impedance caused by the reduction of parasitic MOS capacitance is amplified for high frequency, which explains the variation of S₂₁ and S₁₁ in high frequency is more evident than in low frequency. Based on the resistance-inductance-conductance-capacitance (RLGC) equivalent circuit model, the TID characteristics of parasitic MOS capacitance within TSV structure was verified using Keysight ADS (advanced design system) simulation software. And, it is concluded that the reduction of parasitic MOS capacitance within TSV structure under the effect of TID is responsible for the degradation of signal transmission performance.