Using SOF d-orbital theory of Fe3+-ion in complex, we have calculated the absorption spectra of YIG and YGG:Fe3+ at low symmetry D3d and S4 respectively. With only two parameter N and μ, we have explained the splitting at 10800 cm-1, 21160 cm-1, 25700cm-1, 27600cm-1 in YIG, and pointed out that the peaks at 26320cm-1 and 26970cm-1 in YGG:Fe3+belong to two center transitions of Fe3+-ion pairs. Some confusion in the theory of the absorption specta of YIG and YGG:Fe3+ have been clarified.