Polytitanocarbosilane as the precursor of titanosilicon carbide fiber was synthesized by heating a mixtures of polycarbosilane obtained by the pyrolysis of polydimetheylsilane and polytitanosiloxane prepared by the reaction of diphenylsilanediol with titanium tetrabutoxide. The precursor of polytitanocarbosilane was characterized by IR and NMR, and the molecular weight and solubility characteristics were measured. The activation energy for the depolymerization of polytitanocarbosilane was determined by dynamic TGA data. The depolymerization activation energy for polytitanocarbosilane with the number average molecular weight of 3770 was 67kcal/g-mol.