After cold-rolled deformation of 430 ferritic stainless steel at room temperature with a 55% reduction, the annealing treatments were carried out at 800, 850, 900, 950, and 1000℃ for 15 min, followed by in?situ tensile and nanoindentation tests. The microstructure and mechanical properties of 430 ferritic stainless steel were studied by field emission scanning electron microscopy (SEM), electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). The results indicated when the annealing temperature increased from 800 to 850℃, the recrystallization proportion of the cold-rolled microstructure of the sample gradually increased, the recrystallization proportion increased from 66% to 68%, and the average grain size decreased significantly, from 9.23 μm to 8.07 μm. At this time, the microstructure of the sample was mainly affected by grain refinement, and the strength and plasticity of the sample were improved to a certain extent. The hardness also showed a certain degree of improvement. When the annealing temperature increased from 900℃ to 1000℃, the recrystallization ratio of the cold-rolled specimens increased from 71% to 89%, the average grain size increased by about 1.5 times, the dislocation density decreased significantly, the strength of the specimens decreased while the plasticity increased, and the hardness decreased significantly. When the sample was annealed at 850℃, the grain size in the structure is small and uniform, the yield strength reached 882 MPa, the elongation reached 17.5%, and the hardness value wass 2.08 GPa, indicating good microstructural and mechanical properties. Therefore, the optimal annealing process of 430 ferritic stainless steel was held at 850℃ for 15 min.