Saturated Ca(OH)_2 and AlCl_3 solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as 1100℃. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of 13 nr/g. The measurement of hydraulic exotherm revealed that the exothermal rate is in peak for about 2 h. The exothermal quantities are 449.24 J/g at 12 h and 488.38 J/g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100％ of the 3 days curing strength in the mortar test. Saturated Ca (OH) _2 and AlCl_3 solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as 1100 ° C. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of ​​13 nr / g. The measurement of hydraulic exotherm revealed that the exothermal rates is in peak for about 2 h. The exothermal quantities are 449.24 J / g at 12 h and 488.38 J / g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100% of the 3 days curing strength in the mortar test.