Up to now, the analyses of painted cultural relics based on spectral imaging have mainly focused on pigment analysis, information enhancement and implicit information mining, etc. These imaging methods mainly use remote sensing image processing software. Considering the deficiency of specialized analytical methods for cultural relic data, we propose new spectral imaging-based applications and methods in the analyses of painted cultural relics. These include new applications of restoration area perception based on minimum noise fraction (MNF) rotation using region of interest analysis and fusion to mine implicit information of painted cultural relics and a new method of sketch extraction for painted cultural relics based on sparse non-negative matrix under-approximation. Through experiments on mural paintings, painted clay sculptures and hand-painted silk paintings from Tang tombs, it is found that 1) spectral imaging can effectively perceive mural restoration areas and that 2) the proposed new method can effectively mine hidden information and extract sketches based on spectral imaging. This research on the analyses of painted cultural relics is of great significance.