Abstract: The wind-induced pressure inside buildings has a profound effect on building safety, it can′t be ignored in the wind-resistant design. Base on some reasonable assumptions, the governing equations of internal pressures for building with internal partitioning and openings are derived by the application of the unsteady form of Bernoulli equation, law of mass conservation and adiabatic law, when its background porosity is considered. Influence of the background porosity to internal pressure responses are analyzed from numerical method. The studies results show that wind-induced internal pressure responses of building with internal partitioning and openings can be predicted and analyzed by the governing equations derived in this paper; the internal pressure response in the compartment without an external opening is much higher than that for the other compartment when there is no background porosity; the internal pressures responses in both the compartments are suppressed because of the additional damp of background porosity. All the study achievements can have theoretical and practical values on internal pressure of structures.