An anodized aluminum pressure-sensitive paint (AA-PSP) was used to measure unsteady surface pressure distribution on a wind tunnel model. The AA-PSP has a short response time in the order of 10 (is due to its porous structure. However, it exhibits temperature and humid sensitivities. An effective data acquisition procedure as well as digital image processing algorithm was established to compensate the error from the temperature and humid sensitivities. The temperature distribution on the model surface was measured using a temperature sensitive paint to correct the pressure data from the PSP signal. The error from the humid sensitivity was eliminated using two reference data acquired at dried and moist air conditions, respectively. The present system was applied to measure the buffet phenomena on a delta wing at a high angle of attack in transonic flow, whose flow is unsteady due to the interaction between shock waves and leading edge vortices. The non-periodic unsteady pressure distribution on the delta wing was quantitatively measured with the sampling rate of 1 kHz and within a few-percent uncertainty in absolute pressure level.