Abstract: Vacuum evaporation crystallization to prepare sodium chromate crystal on the basis of the phase diagram of Na2CrO4-NaOH-H2O system at 90 ℃ was introduced.The effects of the crystallization conditions，including stirring intensity， evaporation rate，crystallization temperature，and seed addition etc.，on the process were studied.The optimized operating conditions were determined as follow：the minimum stirring speed to make the crystals suspended from the bottom，the evaporation rate of about 140 mL/h per 1 050 g of raw material，the crystallization medium temperature of 90 ℃，and a certain amount of Na2CrO4 crystal added as the crystallization seeds.Na2CrO4 crystals with large and uniform particle size were prepared under the above optimum conditions.Moreover，the relationship between the boiling point and vapor pressure of the aqueous system with different NaOH concentrations was also investigated，providing a basis for the temperature control during the crystallization process.

Key words: sodium chromate, evaporation crystallization, salting out, phase diagram, boiling point