Abstract: A UNS S31803 duplex stainless steel was treated by solid-solution at 1 573 K and 1 323 K, respectively, and then treated by cold rolling and annealing in sequence. The interfacial boundary character distribution and the susceptibility to intergranular corrosion of the steel were studied by the electron backscattered diffraction and double-loop electrochemical potentiokinetic reactivation method. The relationship between the two properties was analyzed. The results show that after solid-solution at 1 573 K followed by cold rolling and annealing, the equiaxed structure with evenly distributed α and γ phases was obtained in tested steel and a large number of low-energy phase boundaries with K-S and N-W orientation relationship appeared. The percentage of low-angle grain boundaries in α phase was over 50%. These low-energy boundaries hindered the growth of grains, resulting in the improvement of intergranular corrosion resistance of tested steel. After solid-solution at 1 323 K followed by cold rolling and annealing, the microstructure of tested steel was composed of band-like α+γ phases and the phase boundaries with K-S and N-W orientation relationship were relatively few. There were mainly high-angle grain boundaries in α phase. The intergranular corrosion resistance was relatively poor.