The paper investigates the quantum spin Hall effect (QSHE) in silicene, a two-dimensional hexagonal structure with a low-buckled geometry. Using first-principles calculations, the authors demonstrate that silicene can realize QSHE due to its topologically nontrivial electronic structures. The spin-orbit coupling (SOC) opens a band gap of 1.55 meV at low temperatures, which is higher than that of graphene due to the large SOC and low-buckled structure. The gap can increase to 2.90 meV under certain pressure strain. The authors also study germanium, finding that it has a band gap of 23.9 meV, much higher than the liquid nitrogen temperature. The nontrivial topological properties of silicene and germanium are confirmed by direct calculations of the $Z_2$ topological invariant. These findings suggest that silicene and germanium with their low-buckled honeycomb geometry could be promising materials for spintronics and other applications.The paper investigates the quantum spin Hall effect (QSHE) in silicene, a two-dimensional hexagonal structure with a low-buckled geometry. Using first-principles calculations, the authors demonstrate that silicene can realize QSHE due to its topologically nontrivial electronic structures. The spin-orbit coupling (SOC) opens a band gap of 1.55 meV at low temperatures, which is higher than that of graphene due to the large SOC and low-buckled structure. The gap can increase to 2.90 meV under certain pressure strain. The authors also study germanium, finding that it has a band gap of 23.9 meV, much higher than the liquid nitrogen temperature. The nontrivial topological properties of silicene and germanium are confirmed by direct calculations of the $Z_2$ topological invariant. These findings suggest that silicene and germanium with their low-buckled honeycomb geometry could be promising materials for spintronics and other applications.