In this paper, the selective laser melting (SLM) technology was used to prepare Inconel 625 alloy specimens. Gleeble 3800 thermal simulation experimental machine was used to produce Inconel 625 alloy specimens at 700, 800, 900 and 1 000 ℃. The rheological behavior of the alloy at high temperature was studied by isothermal compression experiments at strain rates of 1, 0.1, 0.01, 0.001 s-1, and the real stress-strain curve was obtained. The constitutive model of SLM Inconel 625 alloy was established by Johnson-Cook model and Modified Johnson-Cook model respectively, and the prediction accuracy of the two models was compared. The results show that the error of the original Johnson-Cook model is AARE 83.53% and the correlation coefficient is 0.77. The error AARE of the Modified Johnson-Cook model is 14.87%, and the correlation coefficient is 0.98. The accuracy of the Modified Johnson-Cook model is significantly higher than that of the original model, and it has higher prediction accuracy. The high temperature rheological behavior of Inconel 625 alloy can be well reacted by additive manufacturing. Finally, microstructural analysis of compressed specimens reveals hardening and recrystallization softening, with temperature and strain rate significantly influencing material microstructure.