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Atomically thin 2D material absorbed with a single magnetic atom hold out the promise to overcome the difficulties of bit miniaturization for data storage. One key issue is to find out an appropriate material system with high structural stability and large magnetic anisotropic energy. In this work, we performed density functional calculations for two-dimensional systems with transition metal adatoms on WS₂ monolayer. We demonstrated that Re/WS₂ has a large perpendicular magnetic anisotropy energy, up 30 meV/atom, which is promising for magnetic data storage. Furthermore, the local magnetic moments are introduced in WS₂ and hence cause large valley splitting, and this system is also appropriate for the development of valleytronic devices.