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Aluminum production by carbothermo-chlorination reduction of alumina in vacuum was investigated by XRD, SEM, EDS and thermodynamic analysis. Thermodynamic calculations indicate that AlCl(g) generated by carbothermo-chlorination process among Al2O3-C-AlCl3 system should be at 1 377-1 900 K (100 Pa) and AlCl (g) will disproportionate into aluminum and AlCl3(g) below 950-1 050 K at 10-102 Pa. Experimental results demonstrate that Al4O4C and Al4C3 begin to be formed by Al2O3-C system over 1 698 K (40-150 Pa). It is Al4O4C and Al4C3 but not Al2O3-C that participate in the carbothermic-chlorination reaction. Temperature for AlCl(g) generated by Al4O4C-AlCl3-C, Al4C3-Al2O3-AlCl3 and Al4O4C-Al4C3-Al2O3-AlCl3-C system is 1 703-1 853 K (40-150 Pa). Aluminum metal is produced by AlCl(g) disproportionation process below 933 K. The average purity of aluminum metal reaches 95.32%, which has perfect crystallization and uniform grain size.