Based on the first-principles calculations, the stability, elastic constants, electronic structure, and lattice thermal conductivity of monolayer XO ₂( X= Ni, Pd, Pt) are investigated in this work. The results show that XO ₂( X= Ni, Pd, Pt) have mechanical and dynamic stability at the same time. In addition, the Young’s modulus of monolayer NiO ₂, PdO ₂and PtO ₂are 124.69 N·m ^–1, 103.31 N·m ^–1and 116.51 N·m ^–1, Poisson’s ratio of monolayer NiO ₂, PdO ₂and PtO ₂are 0.25, 0.24 and 0.27, respectively, and each of them possesses high isotropy. The band structures show that monolayer XO ₂( X= Ni, Pd, Pt) are indirect band-gap semiconductors with energy gap of 2.95 eV, 3.00 eV and 3.34 eV, respectively, and the energy levels near the valence band maximum and conduction band minimum are mainly composed of Ni-3d/Pd-4d/Pt-5d and O-2p orbital electrons. Based on deformation potential theory, the carrier mobility of each monolayer is calculated, and the results show that the effective mass and deformation potential of monolayer XO ₂( X= Ni, Pd, Pt) along the armchair and zigzag directions show obvious anisotropy, and the highest electron and hole mobility are 13707.96 and 53.25 cm ²·V ^–1·s ^–1, 1288.12 and 19.18 cm ²·V ^–1·s ^–1, and 404.71 and 270.60 cm ²·V ^–1·s ^–1for NiO ₂, PdO ₂and PtO ₂, respectively. Furthermore, the lattice thermal conductivity of monolayer XO ₂( X= Ni, Pd, Pt) at 300 K are 53.55 W·m ^–1·K ^–1, 19.06 W·m ^–1·K ^–1and 17.43 W·m ^–1·K ^–1, respectively. These properties indicate that monolayer XO ₂( X= Ni, Pd, Pt) have potential applications in nanometer electronic materials and thermal conductivity devices.