Abstract: The microstructure characteristics and evolution behavior, and mechanical properties and its key affecting factors during the hot working process for industrially large-sized plates have been carefully investigated based on a modeled near-α type marine TA31 titanium alloy. The results show that the large-sized TA31 marine titanium alloy plates prepared from different as cast plates of widmannstatten and equiaxed structures and same hot treatment schemes have different structures and properties. The microstructure types of the large-sized marine titanium alloy plates prepared from as cast plates of widmannstatten and equiaxed structures are the same, but the structure states are different. The strength of the plate from as cast plate of equiaxed structure is slightly lower than that of the plate from as cast plate of widmannstatten structure, but its plasticity is higher. Besides, the impact absorbed energies in different positions of the firmer are higher than those in the same positions of the latter. The contents and distributions of primary α and transformed β phases with secondary α laths, and the texture type determine the anisotropy of mechanical properties. The numerical simulation method is adopt to obtain the distribution regularities of temperature field and stress-strain field of TA31 titanium alloy plates, to verify the factors affecting the microstructure evolution and its inhomogeneous distribution. Moreover, the numerical simulation results show that increasing the reduction in pass can help to the transformation to the center of the slab and the broken of the original β grain. The result lay foundation for the optimization of hot-working parameters and the preparation of large-sized marine titanium alloy plate with uniform and stable microstructure.