Abstract: Effect of solution-treated at 900 - 1250℃ on microstructure of steel duplex stainless S32003 has been studied by metallographic, scanning electron microscopy ( SEM) , transmission electron microscopy (TEM) observation and X-ray energy dispersive spectroscopy(EDS) analysis. The results show that the nitride precipitates in steel at 900℃ , in order to dissolve nitride of hot rolling steel, solution temperature must be up to 950 °C ； With the increase of solution temperature , phase content in steel increases α and γ phase content decreases. The optimum solution temperature is 1040℃； As the solution temperature increase, the grain size of α and γ phase is gradually growing up, the grain is obvious coarsening when the temperature is greater than 1100 °C.