The conductivities of InI with different concentrations of Ge-doping have been investigated by the ultra-soft pseudopotential approach of the plane-wave based on the density functional theory under the same condition. Models of the In1-xGexI (x=0, 0.125, 0.25) with In atoms substituted by different fraction of Ge are set up. The optimized structural parameters, total electron density of states, and energy band structures of Ge heavily doped In1-xGexI semiconductors at low temperature are calculated. Results show that the volumes are slightly reduced and the total energies are increased in the In1-xGexI systems and that the systems become instable. As the concentration of Ge increases, the electronic mobility decreases, but the relative number of electrons jumping to the conduction band increases, and the resistivity and the minimum optical band gap increase at the same time, which is beneficial to improving the performance of nuclear detection in the system.