Solar chimneys and tunnel ventilation systems are passive technologies widely recognized for improving indoor environmental comfort. The former leverages solar chimneys to induce natural ventilation through thermal buoyancy, while the latter utilizes subterranean thermal reservoirs to pre-cool incoming air in summer. Existing research predominantly focuses on prototype spaces of solar chimney-tunnel composite ventilation systems, with scant attention devoted to their application in real complex architectures. Therefore, a study of this composite ventilation system based on a complex space is significant to its application in real architecture projects. Drawing on a case study of a Creative Center in northwest China, this research employs Fluent to conduct numerical simulations of the velocity and temperature distributions within the atrium’s solar chimney-tunnel composite ventilation system in summer, complemented by a thermal comfort evaluation. The conclusions underscore the pronounced impact of the coupled effects engendered by the solar chimney-tunnel composite ventilation system on the atrium’s microclimate, gravitating towards comfort thresholds, thereby evincing substantial potential for mitigating air conditioning energy consumption.