Abstract: The mass resolution of Beijing Radioactive Ion Beam Facility Isotope Separator On-Line (BRISOL) is designed of 20 000 for the separation of isobar beam. It is a great challenge for all the elements of the BRISOL facility, including ion source, high voltage, analysis magnets, quadrupoles, and so on. The key technologies of the BRISOL separator and the test results were introduced in this paper. To reach the high mass resolution of 20 000, a bi-energy system was used to reduce energy dispersion which is too large to get high mass resolution. A surface ion source with three electrodes extraction geometry was developed for the BRISOL facility. The RMS emittance of the beam can be optimized to 3.8 πmm•mrad by turning the voltage of the middle electrode. The surface coils were set on pole faces to improve the magnetic field homogeneity. The integral field uniformity with surface coil is optimized to 3.5×10^-5. The β surface coil and γ surface coil were fitted on the pole of big magnet and four electric hexapoles were also used to eliminate the aberration.