A rapid separation system based on SISAK technique was established to isolate 142La successfully from fission products. SISAK technique is often applied in the separation of nuclides with the half-life of
seconds or minutes. Here it was used to separate the parent nuclide of 142La, which the half-life is in the magnitude of several seconds. According to the separation procedure designed in the paper,
the activity of 142La acquired is more than 104 Bq and the decontamination factors for most γ-emitters are higher than 103.