Experimentally synthesized MoSi2N4 (Science 369670 (2020)) is a piezoelectric semiconductor.Here,we system-atically study the large biaxial (isotropic) strain effects (0.90-1.10) on electronic structures and transport coefficients of monolayer MoSi2N4 by density functional theory (DFT).With a/ao from 0.90 to 1.10,the energy band gap firstly in-creases,and then decreases,which is due to transformation of conduction band minimum (CBM).Calculated results show that the MoSi2N4 monolayer is mechanically stable in the considered strain range.It is found that the spin-orbital coupling(SOC) effects on Seebeck coefficient depend on the strain.In unstrained MoSi2N4,the SOC has neglected influence on Seebeck coefficient.However,the SOC can produce important influence on Seebeck coefficient,when the strain is applied,for example,0.96 strain.The compressive strain can change relative position and numbers of conduction band extrema(CBE),and then the strength of conduction bands convergence can be enhanced,to the benefit of n-type ZTe.Only about 0.96 strain can effectively improve n-type ZTe.Our works imply that strain can effectively tune the electronic structures and transport coefficients of monolayer MoSi2N4,and can motivate farther experimental exploration.