The 3-D integration exacerbates the thermal issues over a single die due to the high-power density and poor thermal conductivity of the adhesive layers in between the stackedup dies. In this paper, an electrical-thermal co-simulation is developed to consider the thermal influence and accurately predict the electrical behaviors of the through-silicon-via (TSV) structures. The co-simulation is implemented with the finite element method (FEM) for its capabilities in modeling complex geometries and materials. A highly efficient domain decomposition scheme is introduced into the co-simulation to deal with large-scale massively coupled TSV structures. The domain decomposition scheme enables simulation with multiple processors in parallel and achieves significant reduction in computation time. Various design parameters in typical TSV structures, such as the TSV array in the silicon interposer and the TSV daisy chains are investigated with the proposed co-simulation.