Abstract: The transmission characteristic of radial beam under an immerse focusing magnetic field is analyzed in this paper, and the expression of beam’s axial expansion with the magnetic field intensity is derived theoretically. Then the magnetic field generated by a pair of plane with different current direction and permanent magnet is discussed separately. At last, The magnetic field system based on the plane coils and permanent magnet is designed, with the particle trajectory simulated under stable transmission. Then the theory of magnetic field generated by coils at any point in the space, with the law of magnetic field distribution in a pair of plane coils with different current direction is given. A kind of guiding magnetic field system based on plane coils is designed. The distribution of the magnetic field generated by the guiding magnetic field system along the beam channel and the particle trajectory under stable transmission is researched through simulation.