Abstract-The shimming method used for producing high field homogeneity of the open permanent main magnet for magnetic resonance imaging (MRI) is researched in this paper. The central shimming method based on integer programming is proposed, which fulfills the combination of optimal theory and the practical manual shimming. The formulation of shimming is solved by using Lingo software and the numerical analysis method is used to compute the contribution of small shim arrays. The homogeneity of imaging region is eventually advanced by 50%. The validity of the method is verified by using simulation test of two magnets with different basic magnetic fields. The efficiency of shimming is improved through actual measuring experiment corporated with the manufacturing enterprise.