In order to eliminate the microstructure inhomogeneity of TA19 flash welding joint and improve the comprehensive properties of TA19 flash welding joint. Use Gleeble3500 thermal simulation testing machine on TA19 flash welding head in deformation temperature 900~ 980 ℃, the deformation were 30%, 60%, deformation rate of 0.01 ~ 1 s- 1 for isothermal constant rate under the condition of hot compression test, as to research in welding joint organization under different deformation parameters change characteristics. The experimental results showed that the rheological stress curve of the welded specimen showed a dynamic softening trend during the compression process, and the recovery and recrystallization of the flaked phase were sufficient under the condition of low deformation rate, which promoted the increase of its width and size, and the wedge of phase resulted in the disconnection of the flaked phase. With the increase of deformation amount and deformation temperature, under the action of dynamic recrystallization and element diffusion, the equiaxial ratio of sheet increases gradually. In the process of deformation, residual phases were broken and some mo-rich particles were distributed on the phase matrix. In the subsequent heat treatment process, Mo rich particles on the matrix were dissolved back into phase, which was grown to complete the segmentation of the phase, which was further axialized by static recrystallization. Flash welding specimens under 980 ℃, deformation rate 0.01 s- 1, after 60% deformation under deformation, by 930 ℃ for 1 h + 590 ℃ for 4 h air cooling annealing treatment, can fully realize the weld microstructure of transition such as axis, heat treatment after welding joint organization is given priority to with shaft such as organization, organization uniformity obviously improved.