Abstract: ²⁴²Pu is commonly employed as tracer for determination of ²³⁹Pu in environmental samples. The ²³⁹Pu concentration in Pu(SO₄)₂•4H₂O solution was determined by isotope dilution-mass spectrometry (ID-MS) using a high pure ²⁴²Pu spike. Then the ²⁴²Pu tracer in our laboratary was calibrated by ID-MS using the calibrated ²³⁹Pu solution as spike. By measuring the atom ratio of ²³⁹Pu to ²⁴²Pu twice by ID-MS, the concentration and abundance of the ²⁴²Pu tracer in laboratary were finally calibrated. This method was proved to be efficient with high precision. The process could be finished within two days with an uncertainty of 0.75%. The calibrated ²⁴²Pu tracer in laboratory could meet the demand of high-precision analysis.