Abstract: The DT4E pure iron was annealed at the temperatures of 800-1 000 ℃ for the holding time of 180-360 min. Then the effects of annealing process on the grain sizes, magnetic properties and tensile strength of the pure iron were studied and the optimum annealing process was determined. The results show that the grain size of the annealed pure iron increased with the increase of holding time, and first increased then decreased then increased with the increase of the temperature. With the increase of grain size, the magnetic induction of the pure iron increased while the coercivity and tensile strength decreased. The recommended annealing process was at 850 ℃ for 240-300 min. When treated under this condition, the magnetic induction of the pure iron under the magnetic field intensity of 200, 300, 500, 1 000, 2 500, 5 000, 10 000 A·m-1 was 1.21-1.22 T, 1.30-1.32 T, 1.44-1.46 T, 1.55-1.56 T, 1.67-1.69 T, 1.76-1.77 T, 1.87-1.88 T respectively, the coercivity was 41.32-42.01 A·m-1 and the tensile strength was 306.00-309.33 MPa.