The organic infrared semiconductor ErPc2 prepared by solid phase reaction method has been doped with iodine, the resistivity of ErPc2 has been successfully decreased by about three orders of magnitude by doping. The R-T relationships for intrinsic and iodine doped ErPc2 have been studied, it is found that compared with intrinsic ErPc2, the doped ErPc2 has a remarkable decrease in resistivity, the relationship between resistance and temperature for the doped ErPc2 has not been changed intrinsically, both intrinsic and doped ErPc2 exhibit an exponential dependence of R-T. It is also found that the heat activation energy (Ea) has been effectively reduced by doping, which leads to more carriers that may take part in conducting electricity for ErPc2. The decrease in pre-exponential factor (A) may also contribute to reducing resistivity of ErPc2. The exponential relationship between I and V under a strong electrical field strength has also been explained for the intrinsic organic infrared semiconductor ErPc2.