Abstract: Graphite serves as the principal structures in cores of high-temperature gas-cooled reactors (HTRs), and the irradiation-induced properties as well as mechanical properties are essential to the safe operation of reactors. There are large discrepancies in various graphite grades, resulting in the variations in microstructures and therefore having impact on the irradiation-induced deformation. In this paper, the irradiated behaviors of graphite side reflectors in HTRs were simulated, and the impacts of irradiation-induced deformation of various graphite grades on the irradiation-induced stresses and lives were analyzed. The result shows both the irradiated stresses and lives of graphite structures are strongly dependent on the irradiation-induced deformation. The conclusion could offer an important numerical basis for the structural design of graphite blocks in HTRs.