With the Al(CH3)3 as the precursor of Al elements, two kinds of TiAlC films are prepared by using the atomic layer deposition technique with the TiCl4 and the tetrakis (dimethylamino) titanium (TDMAT) as precursors of titanium elements, respectively, and their film performances are compared and analyzed. The results show that, both these two kinds of TiAlC films are oxidized naturally with different degrees. The optical band gap of films prepared with the TDMAT as precursor has two value of 0.68 eV and 2.00 eV, respectively, while that of the thin films prepared with the TiCl4 as precursor is 0.61 eV. Moreover, the average transmissivity, deposition rate, resistivity, and surface roughness of the former are all higher than those of the latter, while the thickness uniformity of the former is worse than that of the latter. The thin films prepared with the TiCl4 as precursor show an amorphous structure, while in the thin films prepared with the TDMAT as precursor, the TiN crystal appears. Compared with the organic compound TDMAT, the inorganic compound TiCl4 is more suitable as the precursor to prepare TiAlC gate dielectric materials.