The experimental results of X ray diffraction and Doppler broadening of positron annihilation radiation for nanocrystalline material Fe2O3 are presented. It is shown that when samples are annealed at 400°C for 4h and 800°C for 4h

the initial γ -Fe2O3 transforms into the α-Fe2O3

and grain diameters increase to 38.7nm and 92.9nm respectively. The line parameters of the specimen decrease with the annealing temperature. When D～L+

the fraction of free positron annihilation increases obviously. The defect concentration increases slightly for samples compacted with a higher pressure.