Thermogravimetric (TG) analysis provides information related to weight change but is not conclusive enough for direct identification of the composition of the sample in the dynamic thermal process. Raman spectroscopy has the advantage of detecting the composition and phase of the sample. Thermo-Raman spectroscopy (TRS) on the other hand, measures Raman spectra continuously at regular temperature interval for the identification of composition and phase of the species that appear in a dynamic thermal process. Therefore, the composition changes and phase transformations can be studied in the whole dynamic thermal process. Unfortunately, the results obtained from separate thermogravimetric analyzer (TGA) and TRS experiments may not be entirely consistent due to different sampling and experimental conditions. This problem has been overcome by direct coupling of the TGA and TRS instruments in this work so that it is ensured that the experimental and sampling condition do not hamper the results. In this work, coupling of a TGA to a thermo-Raman spectrometer (TRS) for in situ investigation of composition with weight loss have been illustrated using CaC2O4-H2O which is widely used as a calibration standard for TGA. The thermo-Raman intensity (TRI) and differential thermo-Raman intensity (DTRI) thermograms were consistent with those of TG and differential thermogravimetry (DTG) thermograms, respectively.