In this work, droplet breakup in a square-sectioned pulsed disc and doughnut column (PDDC) was investigated experimentally. Droplet breakup was observed by a high-speed online camera. Three different breakup patterns, tensile breakup, popping breakup, and revolving breakup, were observed. In all these patterns, shear stress was the main factor causing the breakup. Breakup frequency function and daughter droplet size distribution function were studied in different experimental conditions. Computational fluid dynamics simulation was used to study the flow field in the PDDC. Particle image velocimetry measurement was performed to verify the simulation results. The shear stress was calculated based on the simulation. The breakup frequency function and daughter droplet size distribution function were then correlated with the shear stress. The calculated results from the correlation equations were in good agreement with the experimental data. The correlation equations were finally applied in a simplified population balance model to calculate the droplet number density function. The calculated number density was in good agreement with the measured results, which further proved the validity of the correlation equations.