In this paper, to verify the applicability of the viscoplastic constitutive model, which was previously proposed by the authors, to the viscoplastic deformation at the high temperatures, a series of tests such as cyclic tension-compression loading with the constant strain amplitude under the constant strain rate and creep tests are carried out at the high temperatures by using oxygen-free copper (OFC). A cyclic tension-compression tests under variations of temperature is also conducted. The experimental results show that the temperature history does not affect stress-strain relations under cyclic tension-compression loading regardless of variations of temperature. Using the material constants determined by the cyclic tension-compression test at isothermal condition, creep and cyclic deformations under variations of temperature can be well simulated by the viscoplastic model.