It is known that, under appropriate conditions, the amplitude of vibration of some blades in the mistuned bladed disk system become large compared to what would be predicted by an analysis of the perfectly tuned system. In this paper, the rms responses of the mistuned bladed disk system subjected to random excitation with the spatial decorrelation and correlations are investigated. The effect of the correlation of the random excitation on the rms response is discussed. It is shown that the rms response of the mistuned system subjected to the spatially-uncorrelated random excitation is almost the same as that of the tuned system. In the case the random excitation is spatially-correlated, it is noted that the rms responses of the mistuned system is much larger than those of the tuned system and that the mistuning configurations effect on the rms responses. With the spatial correlation, it is also noted that the particular mode shapes play an important role in the rms response.