A theoretical study of Th accommodation in Gd2Zr2O7 has been performed by density functional theory. Our calculations show that although thorium has only one charge state of Th4+, it can be incorporated into both Gd3+ and Zr4+ sites in Gd2Zr2O7, depending on the chemical environments. Th occupation at Gd3+ site results in charge redistribution and the excess electrons introduced by Th are transferred to the neighboring Zr ions. As compared with the pure state, Th-containing Gd2Zr2O7 pyrochlores are probably more inclined to undergo order-disorder transformation and are less susceptible to radiation-induced amorphization.