Abstract: The correlations between damping properties and strain amplitude as well as frequency and temperature of the Ni53Ga27Fe20 ferromagnetic shape memory alloy(FSMA)and the Ni53Ga27Fe15Co5 FSMA were investigated by using low frequency torsion pendulum.The effect of Co on damping properties of the Ni-Ga-Fe FSMA was studied.The results show that the microstructure of the Ni53Ga27Fe15Co5 alloy at room temperature was martensite with three forms,and that of the Ni53Ga27Fe20 alloy was martensite with single form.The initial temperatures of martensite transformation and reverse transformation of the former were 59.2℃ and 58.7℃,and the finish temperatures were 35.4℃ and 72.2℃.The initial temperatures of martensite transformation and reverse transformation of the latter alloy were 69.3℃ and 93.6℃,and the finish temperatures were 60.2℃ and 102.6℃.The Ni53Ga27Fe20 alloy was anelastic damping at room temperature.The Ni53Ga27Fe15Co5 alloy was anelastic damping when the strain amplitude was less than 5.0×10-5 and static hysteretic damping when the strain amplitude was more than 5.0×10-5 at room temperature.The temperature of thermoelastic martensite phase transformation of the Ni53Ga27Fe15Co5 alloy was lower than that of the Ni53Ga27Fe20 alloy.The Ni53Ga27Fe15Co5 alloy had high damping properties with the maximum value of 0.072 in the phase transformation temperature range.