Abstract: In the fast reactors, the scattering resonance of intermediate weight nuclide and the space-coupling effects are significant. To solve these problems, this study uses Open MC based on Monte Carlo method to generate the few group constants and combines the deterministic method to do the core calculation. For this analysis, 2D R-Z homogeneous core model was used for the generation of the constants. The assembly calculation shows that the scattering resonance in high energy region can be well dealt with. Both k_eff and power distribution have a discrepancy of less than 1% from the reference solution. Therefore, this hybrid method is suitable for the fast reactor analysis.