The ion source is playing an important role in EMIS(Electro-Magnetic Isotope Separator),and its characteristics decide the capability of the EMIS and the isotope quality.The ion source has arc discharge chamber and extracting electrodes.The focusing electrode of the extracting electrodes extracts and focuses the ion beam,and The ion source is playing an important role in EMIS (Electro-Magnetic Isotope Separator), and its characteristics decide the capability of the EMIS and the isotope quality. The ion source has arc discharge chamber and extracting electrodes. The focusing electrode of the extracting electrodes extracts and focuses the ion beam, and