We have prepared a series of FeCo-Al2O3 nanogramilar films using magnetron controlled sputtering method and have investigated the microstructure, tunneling giant magnetoresistance (TMR) and magnetic properties of FeCo-Al2O3 films by means of transmission electron microscopy (TEM), conventional four probes method and vibrated sample magnetometer. The experimental results showed that all FeCo-Al2O3 films were composed of FeCo granules with equiaxial shape uniformly dispersing in the Al2O3 matrix and the granule size increased monotonically with the annealing temperature. For FeCo (32.8vol.%)-Al2O3 film the size distribution satisfied the log-normal function at low annealing temperature but deviated gradually from the log-normal function as the annealing temperature increased. Meanwhile it was found that the TMR of films with lower volume fraction reached a peak value at a higher annealing temperature and the TMR of films with middle volume fraction reached a peak value at a lower annealing temperature. However for the films with higher volume fraction, TMR dropped dramatically. In addition, the TNTR changed non-monotonically with the annealing time or the granule size and both the susceptibility and saturation magnetization increased with the elevation of annealing temperature for FeCo (32.8vol.%)-Al2O3 films. (c) 2007 Elsevier B.V. All rights reserved.