Fe-C granular films with different Fe volume fraction x, were fabricated using a DC facing-target sputtering system at room temperature and subsequently annealed at different temperatures. X-ray diffraction and selected area electron diffraction analyses indicate that as-deposited and low-temperature annealed (less than or equal to350℃) samples are composed of amorphous Fe and C, and higher temperature annealing makes the amorphous Fe transform to alpha-Fe, which is also confirmed by high-resolution transmission electron microscopy. Magnetic measurements indicate that at room temperature the as-deposited Fe-C (xv=58) granular films are superparamagnetic and annealed ones are ferromagnetic. The coercivity of 100 nm thick Fe-C (xv=58) granular films increases with annealing temperature (for 1h) and time (at 450℃). The coercivity of the 100 nm thick Fe-C (xv=58) samples annealed at temperatures ranging from 400 to 500℃ decreases linearly with measuring temperature T, signalling a domain wall motion mechanism. For the samples annealed at 550℃, the change of in-plane coercivity with T satisfies the relation Hc similar to T-1/2, reflecting that this system behaves better as a set of Stoner-Wohlfarth particles. It was also found that there exists a critical thickness (similar to 133nm) for the 450 oC annealed (for 1 h) Fe-C (xv=58) granular films with thickness in the range 100-200nm, below and above which the magnetization reversal is dominated by domain wall motion and by Stoner-Wohlfarth rotation, respectively.