Abstract: Rational approximation has been used in the traditional neutron resonance self-shielding calculation, making the calculation localized in dealing with simple resonance models. Such approximation will bring obvious error when dealing with complex fuel cell/assembly. In order to improve the resonance calculation precision in complex cases, the subgroup method was combined with method of characteristics, and the equations of this combined method were derived. Based on the WIMSD format 69-group data library, a neutron resonance calculation code named SGMOC was programmed, which can be used in the arbitrary two-dimensional geometry. The numerical results of SGMOC are in good agreement with those of MCNP, and thus SGMOC has high calculation precision and geometry flexibility.