Abstract: ⁸⁵Rb and ⁸⁷Rb isotopes with high enrichment are the core working material of the atomic clock. They can only be separated by electromagnetic isotope separator. The receiver system is an important part of this separator. The parameters of the receiver are different for separating the different isotopes. In order to get the request of the enrichment of isotopes, the parameter of the pocket, the design size and the position of the pocket for separating Rb isotope were calculated. The material and cooling temperature of the pocket were improved. The cooling temperature of the pocket is lower than 25 ℃. The problem of the factor effecting the isotope’s enrichment was solved. And now the receiver was installed in the vacuum chamber of the separator, the experiments of ⁸⁵Rb and ⁸⁷Rb were developed, and the ideal working parameters were confirmed. Finally the enrichment of the isotope is exceeded.