In the process of the continuous straightening during continuous casting, elevated temperature creep and stress relaxation are remarkable. During continuous straightening, temperature of steel billet is very high, where the characteristic of deformation is low strain and low strain rate. Experiments of elevated temperature creep, stress relaxation and elevated tension under the conditions of continuous straightening were carried on Gleeble3500 thermal-mechanical simulation machine and the results indicate that both the creep speed and the stress relaxation speed are very fast in the conditions of continuous straightening. Then metallurgical structures were observed. A lead plate was used to simulate the billet during continuous straightening and then straightening forces were measured. An elasto-viscoplastic model and an elasto-plastic model were built according to the experiment to calculate the straightening forces. The contrast between the calculation results and the measured data shows that ignoring the creep and stress relaxation will result in great errors when calculating the straightening forces in continuous straightening. Carrying researches on elevated temperature creep and stress relaxation and using their characteristics in design has great importance to improve the quality and quantity of billets in the process of continuous casting.