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The 612 aluminates were prepared by liquid phase co-precipitation and mechanical mixing. The effect of sintering temperature on the phases of the 612 (BaO:CaO:Al2O3=6:1:2) aluminate, the sintering mechanism and some chemical reactions during the sintering process were investigated. The shape, particle size distribution and phase transform of the aluminates were studied by scanning electron microscope (SEM), Energy Dispersive Spectrometer (EDS), X-ray diffraction (XRD) and laser particle size analysis. The result shows that the submicron quasi-spherical precursor particles with the D (n, 50)(nm) of 815 nm can be produced through the method of liquid phase co-precipitation. Using the obtained precursor, the 612 aluminates with high degree of crystallization and the crystal phase of Ba5CaAl4O12 can be produced after high temperature sintering at 1500 ℃b. The emission current density for Ba-W cathode (impregnated 612 aluminates) reaches to 15.56 A/cm2 with average evaporation rate of 14.5 nm/h