Deaeration stirrer is the important equipment in the manufacturing processes of aramid fiber. The double helical-ribbon blades of the stirrer are operated in high-viscosity glue. The stiffness of Blades has a strong impact on the effect of deaeration. Usually, the analysis for the fluid-structural interaction problem is a complex problem. However, under the condition of the high viscosity of the glue and uniform rotation of the blades, glue can be treated as a laminar flow and the fluid-structural interaction problem can be simplified. This paper first computes the flow field of blender by solving the Navier-stokes equation in FLUENT and find the pressure distribution on the common face of solid-liquid. Then for the six different thicknesses of blades, the paper computes the displacement and the stress of the blades under the pressure distribution by using ANSYS respectively. The simulation results of the paper are crucial in the design of the blades of the Double Helical-Ribbon Blender.