We investigate the effects of strain on the electronic and magnetic properties of ReS 2 monolayer with sulfur vacancies using density functional theory. Unstrained ReS 2 monolayer with monosulfur vacancy (V S ) and disulfur vacancy (V 2S ) both are nonmagnetic. However, as strain increases to 8%, V S -doped ReS 2 monolayer appears a magnetic half-metal behavior with zero total magnetic moment. In particular, for V 2S -doped ReS 2 monolayer, the system becomes a magnetic semiconductor under 6% strain, in which Re atoms at vicinity of vacancy couple anti-ferromagnetically with each other, and continues to show a ferromagnetic metal characteristic with total magnetic moment of 1.60µ B under 7% strain. Our results imply that the strain-manipulated ReS 2 monolayer with V S and V 2S can be a possible candidate for new spintronic applications.