Electron transfer (ET) rates of a charge localized (Class II) intervalence radical cation of a bis(hydrazine) are investigated theoretically. First, the intramolecular ET parameters, i.e., reorganization energy, electronic coupling, and effective frequency, are calculated using several ab initic, approaches. And then, the extended Sumi-Marcus theory is employed to predict ET rates by using the parameters obtained. The results reveal that the rates of three isomers of [22/hex/22](+), oo(+)[22/hex/22](+), io(+)[22/hex/22](+), and oi(+)[22/hex/22](+), are agreement with the experiment quite well while the rate, of isomer ii(+)[22/hex/22](+) is about 1000 times larger than those of the others. The validity of different ab initio approaches for this system is discussed.