The effect of alloying element(Ni.Co,Mn) on P doped Fe 5.3° low angle grain boundary(GB) embrittlement was investigated by the Recursion method.The model of dislocations was used to construct the atomic structure for the P doped GB.The result indicated that the role of impurity and alloying element segregation to GB can be studied with BOI and the difference between their segregation energies at GB and at free surface(FS)(△E =E_(seg)~(gb)-E_(seg)~(fs)).The BOI results showed that P leads the “loosening” of the 5.3° low angle GB and decreases the cohesion strength of P doped GB when the alloying element(Ni,Co,or Mn) is added into the P doped 5.3° low angle GB.The AE value reveals that the alloying element Ni,Co and Mn have higher energy at P doped 5.3° low angle GB,indicating it serves as a GB embrittler.The BOI results and △E calculation were comparable with each other,and they are also consistent with the experimental results,which confirm the embrittling effect of alloying element(Ni,Co,Mn) on P-induced GB embrittlement. The effect of alloying element (Ni.Co, Mn) on P doped Fe 5.3 ° low angle grain boundary (GB) embrittlement was investigated by the Recursion method. The model of dislocations was used to construct the atomic structure for the P doped GB. The result indicated that the role of impurity and alloying element segregation to GB can be studied with BOI and the difference between their segregation energies at GB and at free surface (FS) (ΔE = E seg ~ gb) -E_ ( The BOI results showed that P leads the “loosening” of the 5.3 ° low angle GB and decreases the cohesion strength of P doped GB when the alloying element (Ni, Co, or Mn) is The AE value reveals that the alloying element Ni, Co and Mn have higher energy at P doped 5.3 ° low angle GB, indicating it serves as a GB embrittler. The BOI results and Δ E calculation were comparable with each other, and they are also consistent with the experimental results, which confirm the embrittling effect of alloying element (Ni, Co, Mn) on P-induced GB embrittlement.