Abstract: Thermo-mechanical reliability of through silicon via (TSV) has become an important factor restricting the market application of TSV. In this paper, the thermodynamics characteristics of coaxial TSV with BCB dielectric layer were studied and analyzed. Meanwhile, in order to reduce the thermal stress of coaxial TSV, different parameters were simulated with various design geometries, including the thickness of SiO<sub<2</sub< insulation layer and shielding ring, the pitch of TSVs as well as the radius of center signal line. The results show that, under the premise of the characteristic impedance match, the thermal stress of coaxial TSV can be effectively reduced by increasing the thickness of SiO<sub<2</sub< insulation layer or decreasing the thickness of shielding ring,while the influence of the radius of the center signal line and the TSV pitch can be neglected.