An attempt is made to explore a low cost, high efficiency and green metallurgical way to produce TiAl Alloy by a reduction-diffusion method in CaH2-TiO2-Al system. Kinetics has been studied based on the possibility of thermodynamics. Under the reaction conditions, CaH2 decomposes into Ca and H-2 firstly, then TiO2 is reduced to Ti by gaseous and liquid Ca, and Al transfers onto the Ti surface by diffusion itself in liquid state, or with gaseous or liquid Ca. The reduced high active Ti reacts with Al to form TiAl. In the reaction process, Al is the main diffuser. The forming process of TiAl can be analyzed by first class liquid-solid contracting core model. The rate-controlling step of the reaction is a liquid-solid interfacial chemical reaction, which can be obviously effected by temperature and time. To increase the reaction temperature or to prolong the reaction time is beneficial to form the TiAl alloy. The reaction activation energy of the reduction-diffusion reaction is 76.84 kJ/mol with an exponential factor of 1.54x10(-2).