In this study, we introduce a real-time vision-based modal testing system to estimate the modal parameters of shell-shaped objects simultaneously using high-frame-rate structured-light-based vision. Based on structured-light-based vision consisting of a DLP LightCrafter projector and a high speed vision platform (IDP Express), the transient three-dimensional (3D) geometry of a vibrating shell-shaped object can be measured in real time at 1,000 fps as the 3D vibrational displacements of 100 points on an object in the audio frequency range. In our system, the modal parameters are estimated simultaneously for the 3D displacements of the shell-shaped object using a fast output-only modal parameter estimation algorithm, SSI-CPAST, on the IDP Express. Therefore, our modal testing system can simultaneously monitor and inspect the input-invariant structural dynamic properties of vibrating shell-shaped objects excited at dozens or hundreds of Hertz. Our system can be applied to real-time vision-based structural damage detection and fatigue testing in various applications. To demonstrate the performance of our vision-based modal testing system, an experiment was performed in real time to estimate the resonant frequencies and mode shapes of steel plates with artificial damage, which were excited at dozens or hundreds of Hertz using a hammer.