Thermal decomposition and deformation of a compact disc-recordable were simulated and observed. From the calculations, the writing power for the dye melting, dye decomposition and the polycarbonate (PC) deformation was predicted, and was experimentally confirmed by atomic force microscope (AFM) observation of the dye layer and PC surfaces. The deformation effects of each layer were evaluated according to the recording characteristic, the carrier to noise ratio (CNR). In the wrting power range of 4.0-6.0 mW, the deformation of the PC substrate contributes to the CNR increase and the PC plays an important role in efficiently improving the CNR.