Improvement in the field emission properties of α-Fe2O3 nanoflakes is observed after high energy X-ray irradiation from synchrotron radiation. Field emission threshold field of α-Fe2O3 nanoflakes is found to decrease from 10.1 to 7.8 MV/m after X-ray irradiation with the dose of 9.0 × 1014 phs/cm2. Electrical measurement reveals that the potential barrier at the back contact between the α-Fe2O3 layer and the iron substrate changes after X-ray irradiation. The observed threshold field decrease is well explained by the changes in potential barrier at the back contact of α-Fe2O3 nanoflakes, which indicates the back contact plays an important role in controlling the field emission properties of α-Fe2O3 nanoflakes. Our study shows that the α-Fe2O3 nanoflakes are a promising material for the application as field emitter under X-ray environment.