Abstract: The influence of the second stage polymer melt rheological parameters on the fluid-solid coupling interaction and fluid-solid coupling deformation of the first stage polymer micro-component were systemically studied using finite element numerical simulation, and the mechanisms were finally revealed by theoretical analysis. Research results showed that the fluid-solid coupling interaction between second stage melt filling flow and first stage polymer solid micro-component became enhanced with increasing melt zero-shear viscosity of second stage，which in turn increased the micro-shaft of fluid-solid coupling pressure and uniformed the temperature field. Therefore, the bending stress and deformation of first stage micro-shaft depended on fluid-solid coupling pressure increases, but the thermal stress and deformation depended on temperature field uniformity reduces.

Key words: in-mold assembly molding, micromachine, fluid-solid coupling, numerical simulation