Abstract: On the basis of a bending magnet and a quadrupole doublet, a beam transport system isdesinged. It will be used in separating and purifying secondary radioactive beams of ions such as~6He, ~7Be, ~8Li, ~(11)C, ~(12)B, ~(13)N, ~(15)O and ~(17)F. The parameters, which may affect the systemperformance, are optimized by using TRANSPORT code. The purification of secondary beams isdiscussed in detail.