This study is to investigate how to realize the fixed proportional tension-torsion loading test in the life cycle of solid cylindrical shaft. The route of loading control is based on the theory of elastic stress ratio (C(?/?)) with the consideration of true stress and strain. The PID control method is used in the tension-torsional testing machine. 24 series of experiment has been done in different C with 24 specimens of 16MnR and 304 stainless steel. A ratio correction coefficient (C?) is put forward depend on the true stress strain ratio ( / ) and experiment results. The results show that: the control route based on C is accurate when the specimen in elastic phase. The difference of between 16MnR and 304SS is related to control method, but not related to specimen when the material gets to large plastic deformation. The accuracy of the fixed proportional tension-torsion loading test in the life cycle was increased when the C? was applied to control procedure.