Abstract: A theoretic equation of deformation work, phase transformation temperature, initial grain size and metal structure was analyzed, and a method of controlling the precipitation of σ phase was provided. On this basis, the properties and microstructures of SAF2205 duplex stainless steel during isothermal hot tensile tests were investigated by means of stepped isothermal tension. The result shows that, with the method of fast cooling and temperature-changed isothermal hot tension, the precipitation of σ phase can happen during the deformation, and the tiny and dispersed σ phase can limit the growth of the grains. In order to realize the strain-induced precipitation of σ phase and the superplastic deformation of duplex stainless steel in lower temperatures, a faster cooling velocity needs to be applied.