In this paper, we studied the internal friction behaviour of Fe-13at%Ga. It is found that the internal friction behaviour of the alloys shows high sensitivities to thermal history and measuring conditions. In the low temperature range, the damping capacity of the alloys raised greatly after heat treatment. We can concluded that the low-temperature internal friction can be attributed to the phase transition and magnetomechanical hysteresis caused by the irreversible motion of magnetic domain while the high-temperature IF peak with typical relaxation natures originates from the grain boundary relaxation.