Abstract: Equations to describe the internal pressure dynamic response for an opening structure with two compartments were set up. Resonance frequency and equivalent damping ratio are also deduced. The wind tunnel investigation on the dynamic behavior of internal pressure was applied to a series of two-compartment models with different opening ratios and volume ratios between two compartments. Test results show how to correctly simulate wind induced internal pressure response in a two-compartment building, and that the internal volume of the test model should be adjusted by the square of full scale to the model velocity ratio in a wind tunnel test. Lower pressure root-mean-square (RMS) is observed in the compartment with an external opening (front compartment), relative to the one without an external opening (back compartment). The internal to external pressure RMS ratio grows as the increase of the compartment opening ratio and the increased opening ratio will also raise a resonance frequency but reduce an equivalent damping ratio. Although a bigger compartment volume ratio results in a higher first-order resonance frequency and a lower second-order resonance frequency, both of them are more close to the Helmholtz frequency of an opening structure without internal partitioning.