In recent years, the state-of-art first-principles computational approach has emerged as an effective tool to discover unknown topological properties in the existing materials.The ability to create and manipulate these topological states is of vital importance for designing next-generation quantum electronic devices.In this talk, I will present: (1) Light-induced type-Ⅱ band inversion and quantum anomalous Hall state in monolayer FeSe.Depending on the handedness of light, a spin-tunable quantum anomalous Hall state with a high Chem number of ±2 is realized.Our finding affords an exciting opportunity to detect Majorana fermions in one single material without magnetic doping.(2) Pressure-induced organic topological nodal-line semimetal in the three-dimensional molecular crystal Pd(dddt)2.Depending on the hydrostatic pressure, an intriguing F-centered nodal line, without protection from any crystal symmetry, is generated by accidental band degeneracy.Our finding affords an attractive route for realizing fancy organic topological states in 3D molecular crystals.