The electronic structures and magnetic properties of strained monolayer MnPSe3 are investigated systematically by first-principles calculations. It is found that the magnetic ground state (GS) of monolayer MnPSe3 can be significantly affected by biaxial strain engineering, while the semiconducting characteristics are well preserved... Owing to the sensitivity of the magnetic coupling towards the structural deformation, a biaxial tensile strain about 13% can lead to an antiferromagnetic-ferromagnetic (AFM-FM) transition. The underlying physical mechanism of strain-dependent magnetic stability is mainly attributed to the competition effect of direct AFM interaction and indirect FM superexchange interaction between the nearest-neighbor (NN) two Mn atoms. In addition, we find that FM MnPSe3 is an intrinsic half semiconductor with a large spin exchange splitting in conduction bands, which is crucial for the spin-polarized carrier injection and detection. The sensitive interdependence among external stimuli, electronic structure and magnetic coupling suggests that monolayer MnPSe3 can be a promising candidate in spintronics. (read more)