  An extensive numerical study is reported on disorder effect in
two-dimensional d-wave superconductors with random impurities in the unitary
limit. It is found that a sharp resonant peak shows up in the density of states
at zero energy and correspondingly the finite-size spin conductance is strongly
enhanced which results in a non-universal feature in one-parameter scaling.
However, all quasiparticle states remain localized, indicating that the
resonant density peak alone is not sufficient to induce delocalization. In the
weak disorder limit, the localization length is so long that the spin
conductance at small sample size is close to the universal value predicted by
Lee (Phys. Rev. Lett. {\bf 71}, 1887 (1993)).
