Abstract: Numerical simulation of the forming process of Ti55531 titanium alloy was carried out.The stress, strain fields and temperature field during the forming process of forgings under different deformations were analyzed, and the evolution of the structure of different parts of the blank during forming was studied experimentally.The results show that the grain size of the easy deformation zone increases with the increase of the degree of deformation or the increase of temperature when the blank is formed, especially at high deformation velocity (20 mm/s)or high deformation temperature (835℃), the grain size increases significantly due to the temperature rise effect of the superimposed deformation heat.The grain size in the difficult deformation area has the largest fluctuation, and there are a few abnormally grown grains.The grain size of the free deformation region remains essentially unchanged.When the deformation rate is 5 mm/s and 10 mm/s, the deformation amount is 50%, and the deformation temperature is 805℃, the alloy's tensile strength, total impact work and crack forming work are all higher, and the comprehensive mechanical properties are better.