This study was carried out to investigate the influence of variations in the temperature and time of isothermal heat treatment, applied stresses and prestrain on the isothermal transformation behavior of ${gamma}$ and ${sigma}$ phases and mechanical properties of 25Cr-7Ni-3Mo duplex stainless steel. The precipitation of ${gamma}$ and ${sigma}$ phases through isothermal heat treatment showed the type curves with a certain incubation period, the curve migrated to in a short period of time and the amount of precipitation increased with decreasing isothermal heat treatment temperature. Under the state of isothermal transformation, the precipitation of ${gamma}$ and ${sigma}$ phases was stimulated by applied stress, with increasing applied stress, the curves migrated to in a short period of time and also observed that the application of stress has a greater influence on the amount of ${sigma}$ precipitation than that of ${gamma}$ precipitation. The precipitation of ${gamma}$ and ${sigma}$ phases was stimulated by cold and warm rolling before isothermal heat treatment and precipitation of ${gamma}$ and ${sigma}$ phases has a greater influence on the warm rolling than cold rolling. The tensile strength and hardness increased with increasing cold and warm rooling reduction ratio.