Abstract: The stress relaxation tests were carried out for GH4169 alloy at temperatures of 450–550 ℃, time of 600 h and initial stress of 800 MPa, and the stress relaxation behavior was analyzed. The relationship between stress and time was fitted by using the cubic delay function. The threshold stress was introduced to modify the Arrhenius creep constitutive model. The stress relaxation curves were obtained by unmodified and modified models and were compared with the test results. The results show that the remaining stress of GH4169 alloy after stress relaxation tests first decreased and then increased with the increase of temperature, and the stress relaxation amounts at 450,500,550 ℃ were about 12,18,15 MPa, respectively. The constructed cubic delay function could accurately describe the relationship between stress and time of GH4169 alloy, with the fitting correlation coefficients all greater than 0.999. The stress relaxation curves of GH4169 alloy at medium temperature simulated by modified Arrhenius model with introducing threshold stress were in good agreement with the test results, with the maximum relative error of 0.02%. The stress relaxation curves simulated at 500 ℃ and 550 ℃ based on unmodified Arrhenius model had a larger deviation from the test results, and the maximum relative error was 0.1%. The modified Arrhenius model could better predict the stress relaxation behavior of GH4169 alloy at medium temperature.