Abstract: As China's urban regeneration continues, old industrial buildings are being renovated in full swing. At present, the renovation mainly focuses on function replacement, architecture form, and spatial layout, but it fails to consider the improvement of indoor physical environments, which thus leads to poor daylighting in buildings in use. In addition, related research in China does not analyze the indoor daylighting effect of renovated old industrial buildings or the optimization strategy for multi-factor variables. This paper took the dining hall in Sesame Street in Zhengzhou as the research object, found the problems through field investigation and measurement, and selected an appropriate optimization strategy. Furthermore, the paper carried out simulation analysis and verification through GBSWARE software simulation and orthogonal experiment and performed comprehensive evaluation in terms of daylighting factor, dynamic daylighting hours, and daylighting compliance rate in inner areas, so as to obtain an optimal factor combination under boundary conditions. The results show that the size of an atrium is a significant factor for indoor daylighting optimization of renovated old industrial buildings with large spans, and the atrium can effectively improve indoor natural daylighting.