In this paper, thermo-gravimetry (TG) and differential scanning calorimetry (DSC) are used to investigate the thermal stability of two kinds of the azo dyes in optical storage and optical recording mechanism. The TG analyses take place in a narrow temperature range. The DSC analyses show the rapid exothermic conversion having a threshold. The steep and large weight reduction, litter remains and definite threshold of the dye decomposition are of advantage to the optical recording signal modulation. It is demonstrated that TG and DSC are powerful tools to investigate the optical recording media.