The present invention relates to the magnetic apparatus for magnetic resonance imaging system and method for forming uniform magnetic field. The magnetic apparatus comprises a field yoke for forming flux path, a first member of permanent magnet, provided on one end of the field yoke, free end of which is inclined inwardly, a second member of permanent magnet, provided on the other end of the field yoke in symmetry with the first member of permanent magnet, having reverse polarity with the first member of permanent magnet, an adjusting block, provided on the center of the field yoke for extruding magnetic field formed by the first and second members of permanent magnet. The adjusting block in the present invention can form a magnetic field for adjusting to extrude the basic magnetic field in order to provide a parallel magnetic field. The present invention can be applied in the MRI system and make the system have a high open degree for operations. The MRI system can be made compact, movable and inexpensive.