Abstract: A series of uniaxial tension and relaxation tests were completed at temperatures from 20 ℃ to 700 ℃. The results show that, the tensile constitutive curves of the alloy present obvious yield breaks, subsequent yield hardening in the temperature range from 20 ℃ to 500 ℃ and softening in the range from 500 ℃ to 700 ℃. The elastic modulus, strength and percentage elongation of the alloy in the rolling direction are closed to those of the alloy in the transverse direction, but percentage reduction of area of the uniaxial specimen in the transverse direction is somewhat large. With increase of temperature, elastic modulus and strength of the alloy decrease, and percentage elongation and percentage reduction of area increase. It is seen that the percentage elongation has a sudden reduction in the temperature range from 350 ℃ to 450 ℃. The elevated temperature makes properties of the alloy to have strong sensitivity of strain rate under strain loading. The sensitivity of strain rate is slightly affected by the variety of tempera-ture below 300 ℃ and the alloy behaves least sensitivity to strain rate at 350 ℃. Subsequently, the sensitivity of strain rate enhances with increase of temperature. The influence of temperature on stress relaxation effect of N18 alloy is outstanding. The influence of the variety of temperature on the maximum of stress relaxation is unobvious below 300 ℃, and with increase of strain level the maximum of stress relaxation reduces obviously. Conversely, the strain level is higher, the extent of the maximum of stress relaxation is larger in the temperature range from 350 ℃ to 550 ℃. About 350 ℃, the maximum of stress relaxation reaches minimum value. In the range from 350 ℃ to 450 ℃, N18 alloy presents characteristic of dynamic strain aging obviously.