Iron (Fe) films with a thickness ranging from 1.0 nm to 80.0 nm are deposited on silicone oil surfaces by a vapor phase deposition method. The films with a thickness of d < 2.0 nm do not exhibit planar morphology but ramified aggregates instead. Magnetic force microscopy studies for the Fe films (10.0 nm ≤ d ≤ 80.0 nm) show that the domain wall structure is widespread and irregularly shaped and the oscillation phase shift Δθ, which records as the magnetic force image, changes from 0.29° to 0.81°. Correspondingly, the magnetic force gradient varies from 1.4 × 10−3 to 4.0 × 10−3 N/m, respectively. In our measurement, the characteristic domain walls, such as Bloch walls, Néel walls and cross-tie walls, are not observed in the film system clearly.