Abstract: A new method for determing calcium in nuclear grade sodium is investigated. The matrix sodium is separated by vacuum distillation at the temperature of 380 ℃ and under the vacuum of 6×10-4 Pa. The calcium in residue is dissolved and analyzed by ICPAES. The analysis range of the method is 2.5100 μg/g. The relative deviation of determined samples is ＜5%. This method has been applied to determine concentration of calcium in nuclear grade sodium and sodium sample from purification technology procedure in sodium production factory.