The effect of stress on the magnetic properties of FeCoSiB amorphous films is investigated. It has been observed that the unstressed sample is isotropic in the film plane. The samples under tensile stress show clear easy axis along the stress while the samples under compressive stress show easy axis perpendicular to the stress axis. With increasing of the tensile stress, the coercivity of the films decreases monotonically. The coercivity increases with increase of the compressive stress when the stress is not large and then decreases with further increase of the compressive stress. The variation of the coercivity with stress is understood by taking into account the influences of stress on the rotational and wall displacement magnetization reversal processes.