Abstract: The thermal decomposition of TiD_1.92 powder to titanium was investigated by means of thermal analysis and theoretical calculation. The model that considers bulk and surface processes during desorption shows three kinds of peak in the spectrum. They are all related to phase transformation. The calculated spectrum of spheres particle model is different from the spectrum of planar particle model for their different diffusion models. The decomposition behavior of TiD_1.92 by thermal analysis is consist with the result of planar particle model, the rate controlling process in δ-Ti and β-Ti is the reaction between hydrogen atoms to form gaseous molecules on the surface, and the rate controlling process of decomposition during β→α transform is the deuterium diffusion in α-Ti. Arrhenius plots of experiment data give 152.8 kJ/mol of the surface reaction activation and 68.6 kJ/mol of the deuterium diffusion activation in α-Ti.