Abstract: In order to get the decay data of ⁹⁰Rb measured more accurately, a sample of ⁹⁰Rb of radiochemical purity has to be prepared. A separation method was established based on twice delay separation method, in which the high isotope abundance can be extracted from new produced fission product. First of all, the gaseous fission product ⁹⁰Kr was extracted from the irradiated target by a deflation procedure, and then through a washing procedure, the ⁹⁰Rb generated by ⁹⁰Kr decay was collected. A system for rapid extracting ⁹⁰Kr was also developed. Finally, a carrier-free ⁹⁰Rb product of high specific activity was obtained. The total recovery of ⁹⁰Rb is about 20%. The decontamination factor of the main impurities is about 10³. The whole procedure costs in 2.5 min.