The electric structure and optical properties of monolayer MoS1.89X0.11 have been calculated by the first-principle pseudo-potential method based on density functional theory (DFT). The results show that monolayer MoS1.89X0.11 (X=P, Si, Al) turn to a p-type semiconductor and the conduction band bottom is moved to the direction of low energy. The band gap of monolayer MoS2 of P-doped and Si-doped is turned from K-point to Γ point in the BZ. The band gap of monolayer MoS2 of Al-doped turned to an indirect semiconductor at K -Γ point. Through analyzing the density of states and decentralization of grid, the optical properties of monolayer MoS2 is changed for the variation of carrier concentration and the hybrid orbitals of impurity atoms with S-3p and Mo-4d, especially Al-doped is the most effect that the static dielectric constant and refractive index is increased and the energy loss function is reduced.