In this paper, the effects of Eu, Nd doping, and Eu–Nd co-doping on the stability, magnetic and optical properties of monolayer MoS2 are investigated by the density functional theory based on the first principle's calculations. It was found that the Eu–Nd co-doped monolayer MoS2 is more stable than other considered doping structures. After the introduction of Eu and Nd atoms, the band gap are decreased to different degrees, indicating that the doping is favorable to the electronic jump, which might enhances the conductivity of the system. All doped systems exhibit magnetic properties. In addition, the absorption spectra of all doped systems show significant red-shift compared with those of pure monolayer MoS2, indicating that the doping improves the absorption capacity in visible light. These results might provide theoretical guidance for the design of novel monolayer MoS2 semiconductor materials.