The (g 0 -Fe 4 N/Si-N) n (n: number of layers) multilayer films and g 0 -Fe 4 N single layer film synthesized on Si (1 0 0) substrates by direct current magnetron sputtering were annealed at different temperatures. The structures and magnetic properties of as-deposited films and films annealed at different temperatures were characterized using X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. The results showed that the insertion of Si-N layer had a significant influence on the structures and magnetic properties of g 0 -Fe 4 N film. Without the addition of Si-N lamination, the iron nitride g 0 -Fe 4 N tended to transform to a-Fe when annealed at the temperatures over 300 8C. However, the phase transition from g 0 -Fe 4 N to e-Fe 3 N occurred at annealing temperature of 300 8C for the multilayer films. Furthermore, with increasing annealing temperature up to 400 8C or above, e-Fe 3 N transformed back into g 0 -Fe 4 N. The magnetic investigations indicated that coercivity of magnetic phase g 0 -Fe 4 N for as-deposited films decreased from 152 Oe (for single layer) to 57.23 Oe with increasing n up to 30. For the annealed multilayer films, the coercivity values decreased with increasing annealing temperature, except that the film annealed at 300 8C due to the appearance of phase e-Fe 3 N.