Abstract: Microsystem packaging needs to comprehensively consider the multiphysical coupling of electrical, thermal, and mechanical properties. Taking a 2.5D microsystem packaging structure as the research object, the accuracy of the 2.5D microsystem packaging simulation model was verified through actual testing, and then its key component-TSV interposer (Through-Silicon-Via, TSV) was electro-thermal -mechanics multiphysics coupling simulation analysis. Comprehensive analysis of the electrical, thermal and mechanical properties of the TSV interposer. The simulation results show that the electrical signal transmission efficiency of the initial TSV interposer structure is only 73%, the local temperature is as high as 122.3℃, and the deformation caused by heating is 2.24um. The structural deformation caused by the electrical-thermal coupling reduces the electrical signal transmission efficiency by 6%. Combined with Hammersley's experimental design method, genetic algorithm and other optimization theories, the TSV adapter plate structure is designed for multi-physics collaborative optimization. The results show that the optimized TSV interposer insertion loss S21 is reduced, the electrical signal transmission efficiency is increased to 80%, the maximum temperature is reduced by 18%, and the maximum deformation is reduced by 19.6%.