Constitutive behavior of nickel-titanium shape memory alloy (Ni-Ti SMA) under hot deformation was investigated by means of the compression tests and the linear fitting method. Based on the true stress-strain curves of Ni-Ti SMA under compression at the strain rates of 0.001-1 s−1 and at the temperatures ranging from 600 to 1 000 °C, the constitutive equation of Ni-Ti SMA with respect to the Zener-Hollomon parameter was established according to the high stress level and the low stress level at various temperatures so as to more accurately describe the deformation behavior of Ni-Ti SMA during hot working. Dynamic recovery and dynamic recrystallization of Ni-Ti SMA occur under hot compression, which lays the theoretical foundation for understanding the constitutive behavior of Ni-Ti SMA.