In order to solve the adverse influence caused by ill-conditioned data on damage identification and condition assessment, the monitoring data prediction method based on data correlation was presented in this paper. The correlation degree between multi-channels data was established by BP neural network, and the ill-conditioned data channel was predicted and corrected by the correlation degree between the data, which was verified by the measured data. The results indicate that more accuracy and engineering requirement could be achieved using BP neural network prediction method considering the correlation degree between multi-channel data.