Volute casing is one of the important components in centrifugal pumps. The strength and stiffness of the volute casing made of PMMA used for PIV measurement were investigated by fluid-structure interaction (FSI) simulation in consideration of the impeller-volute interaction. The distribution of pressure and shear stress on the inner surface of the volute casing was obtained by FLUENT. Pressure, gravity and shear stress were imposed on the volute casing, and its stress and displacement distributions under different working conditions were obtained using ABAQUS. The results indicate that in comparison with pressure, gravity and shear stress have negligible influence on volute casing deformation. The volute casing is structurally safe under design condition, and its maximum rotational speed can reach to 1690r/min. At this rotational speed, the maximum displacement of the volute casing is 4.6mm, and measurement error caused by refraction is about 0.11%. Furthermore, two methods for improving the volute casing structure were put forward in consideration of light decay as well as the strength and stiffness of the volute casing.