Abstract: During long-term operation of the dam, due to problems such as instrument failure or equipment transformation, monitoring data will be distorted or missing, which is easy to cause misjudgment of structural safety．Missing monitoring data were interpolated with principle of spatio-temporal correlation, and singular value was identified and processed by combination method of Grabus-wavelet denoising．Reconstructed monitoring data of the dam body were obtained, and singular value was corrected．Example proved that this method could effectively interpolate missing deformation data and calibrate singular value to make monitoring data more scientific and reasonable．