Abstract: To study the influence of strain rate, deformation temperature, and strain on the microstructure and mechanical properties of Cu-Sn alloys, high-temperature and high-pressure tests were conducted using a Gleeble-3800 high-temperature simulation test apparatus at temperatures ranging from 550 to 700℃ and strain rates from 0.001 to 10 s^-1. The true stress-strain relationship of copper-tin alloys at different temperatures was investigated, and a new Johnson-Cook (JC) constitutive relationship was established accordingly. The study shows that during deformation, the rheological stress of copper-tin alloys increases with the deformation rate and temperature. Using the traditional JC model for prediction, the mean relative error (AARE) and correlation coefficient (R) were 34.698 7% and 0.969 6, respectively. With the improved JC model, the AARE and correlation coefficient R were 7.896 7% and 0.972 7, respectively. Therefore, the improved JC constitutive relationship better matches the experimental data and can more accurately reflect the rheological properties of copper-tin alloys at high temperatures.