The influence of spherical resonant cavity on the radiative characteristics of silver was studied, and the results show that the absorptance is increased in the resonance wavelength. As for a good conductor, the absorption spectrum of silver shows the feature of narrow-band absorption. The absorption peak of the resonance wavelength was shifted to the long wavelength compared to the peak of the resonance wavelength formed by a perfect conductor. Due to the presence of skin depth, the resonant cavity was equivalent to a resonant cavity formed by a perfect conductor with a slightly larger size. With computational results, the effects of structural parameters such as the depth of the resonant cavity, the radius of the cavity, the lattice period, the incident angle and the polarization angle on the absorptance of the spherical resonant cavity were discussed. The results indicate that the optimal narrow-band absorption effect can be obtained by reasonably designing the structure size of the spherical resonant cavity and this implies an effective approach for fabricating narrow-band emitter.