Abstract: An investigation was made regarding the variation in internal friction and modulus with 86.4%Mn and 80.8%Mn γMnFe alloys. The results indicate that γMnFe alloys undergo paramagnetic to antiferromagnetic transition and martensitic transformation while cooling from high temperature. There are three internal friction peaks during this process and they all have amplitude effect. It confirms that the twins caused by anteferromagnetic transition and martensitic transformation are the physical nature of high damping capacity of γMnFe alloys.