In order to identity the effect of narrow composition control on the hot plasticity of duplex stainless steel, hot rolling test of OCr25Ni7Mo4N steels with various oxygen, nitrogen and nickel contents were performed at 1200 ℃ for 4 steps. The microstructures and inclusions were observed by OM, SEM and EBSD. The steels with the lowest oxygen, nitrogen and nickel contents showed excellent hot plasticity. The inclusions in the steel with 0.0059% oxygen were mainly Al₂O₃ and MgO·Al₂O₃, which distributed in the grain interior and did no harm to the hot plasticity of the steel. The steels containing 0.038% and 0.046% oxygen actually cracked at the sheet edge during hot rolling, which resulted from the large inclusion particles of Cr₂O₃ and MnO₂ at the α/γ boundary. Furthermore, the reason for more serious cracking occurred in the steel containing 0.038% oxygen than that containing 0.046% oxygen was its relatively higher contents of nitrogen and nickel, making γ volume fraction of the steel as high as 60% in the hot rolling state. Excessive γ reduced its total strain, so that the inadequate stain did not induce the recrystallization of γ phase, which resulted in hot rolling cracking finally.