Abstract: Resonance self-shielding calculation is a very important part of the reactor core design calculation. The traditional self-shielding model can only simulate the simple geometry. The subgroup self-shielding model developed by A. Hebert was utilized to develop a self-shielding calculation code. It can treat complicated geometry with two resonant isotopes contained in fuel region. Numerical results presented for many problems show that this model can get high accurate results when the fuel enrichment is low.