Stainless-steel 316L is one of the widely used structural materials in the nuclear industry, because of its excellent corrosion resistance and mechanical properties. However, very few researches can be found on its viscoplastic behavior and microstructure evolution at warm and hot deformation conditions, which hinder the possible application of advanced manufacturing technologies for producing complex parts, such as superplastic forming or hydroforming. The aims of this study are to explore the stainless steel 316L viscoplastic behavior to determine its strain rate sensitivities and to reveal its underlying microstructure evolution; these will allow appropriate manufacturing (forming) technologies and the optimal forming condition to be determined. Hence, isothermal tensile tests at 700℃, 800℃, 900℃, and 1000℃ at the strain rates of 0.01 s^-1 and 0.001 s^-1 have been carried out. Also, the corresponding microstructure evolution including the grain orientation and geometrically necessary dislocation density have been revealed by electron backscatter diffraction method. The data show the viscoplastic behavior of stainless-steel 316L under various thermomechanical deformation conditions and how the microstructure evolution influences the viscoplastic flow stress.