This study uses wind tunnel experiments to investigate wind-driven cross ventilation in partitioned buildings. The discharge coefficients of internal opening under various flow conditions were determined by a fan technique. It was found that the internal discharge coefficient is dependent on the internal porosity, but independent of external porosity, and opening location. Based on the experimental results, a predictive model for internal pressure and ventilation rate of multi-room buildings was developed and verified. This model also revealed that the ventilation rate increases as the internal porosity increases, and that the maximum ventilation rate occurs when the windward and leeward opening areas are equal. Because internal partitions reduce the difference between external and internal pressure, the ventilation rate of partitioned buildings is always smaller than that of buildings without partition. Furthermore, this study provides a quantitative scheme to regulate the ventilation rate of partitioned buildings by controlling the opening areas of windward, leeward and internal openings.