Abstract: This paper investigates the tensile properties of cashmere fibers and the tensile relaxation of cashmere single yarn in comparison with those of super-fine merino wool and wool yarn.It shows that the specific tenacity,tensile modulus and relaxation time of cashmere fiber are higher than those of wool;the relaxation rate of tensile stress of cashmere yarn is lower than that of wool yarn under the condition of small constant rate of extension,that is,cashmere yarn is more difficult to setting than wool yarn.These differences in mechanical properties between cashmere and wool fibers are resulting from that the-αcrystallinity of cashmere fiber is higher than that of wool.At different temperatures from 80℃to 130℃,the relaxation rate of tensile stress and degree of setting increase with the rising of temperature.However,when temperature is above 120℃,the increase of relaxation rate and degree of setting is not remarkable with the higher temperature.