Isothermal constant strain rate compression of Ti₂AlNb-based alloys was carried out using a Gleeble-3500 thermal simulation tester with deformation temperatures of 650-850°C, strain rate interval of 0.001–1s^-1, on the basis of which a modified Zerilli-Armstrong model and an optimised Zerilli-Armstrong model were developed to describe the thermal deformation behaviour of Ti₂AlNb-based alloys. The results show that the error between the predicted and experimental values of the modified Zerilli-Armstrong model is larger, with correlation coefficients R and E_AR of 0.935 and 12.4% respectively, while the optimised Zerilli-Armstrong model can predict the flow stress better, with correlation coefficients R and E_AR of 0.964 and 10.5% respectively. The optimised Zerilli-Armstrong model had high prediction accuracy and wider applicability, making it more suitable as a constitutive model for predicting the thermal deformation behaviour of Ti₂AlNb-based alloys.