A permanent magnet biased radial magnetic bearing with external rotor for vacuum tube was introduced, and the configuration and operating principle were analyzed. The parameter design method based on the total magnetic flux was established to deduce the calculation formulas of the parameters of the permanent magnet radial magnetic bearing. The magnetic flux leakage coefficient and the magnetic resistance coefficient were considered, and the calculations were constrained to the degree of magnetic flux density unsaturation of the internal magnetic field of the soft magnetic material. Finite element software was used to execute simulation analysis and modeling of the permanent magnet biased radial magnetic bearing. The results show that the design method is reasonable and efficient, and the design magnetic bearing is compact and easy to control, which is more suitable for the liner motion with low power consumption.