In this research, based on the back propagation neural network (BPNN) model and particle swarm optimization with linear decreasing inertia weight (PSO-LDIW) algorithm, an electro-thermal and thermal-stress fields coupling optimization design method for coaxial through silicon via (CTSV) is provided. The irregular and complex relationship between the parameters (height of CTSV, radius, thickness of SiO2, BCB and coaxial annular) and indexes is investigated by COMSOL Multiphysics and HFSS software. According to the simulation data of COMSOL and HFSS, the BPNN models are used to express the corresponding relationship between the parameters and indexes of CTSV. According to the desired indexes of CTSV, the multi-objective optimization function is formulated. Then, the PSO-LDIW algorithm is applied to optimize the parameters of CTSV. Finally, the simulation experiment is used to verify the effectiveness of the optimization design strategy. The simulated indexes (-40.28 dB, 366.31 K, 115.21, 74.14 and 23.16 MPa) well consent to the desired ones (-40 dB, 360 K, 110, 70 and 25 MPa), which indicates that the parameters of CTSV can effectively optimized by the developed design method to control the indexes. Therefore, the developed electro-thermal and thermal-stress fields coupling optimization design method can effectively design CTSV for manufacturing high-performance Chiplet-based microsystem.