The solute equilibrium partition coefficients (ki) of C, Si, Mn, P, and S in high sulfur steel during the solidification process were investigated by the thermodynamic calculation. The effect of MnS precipitation on ki was explored. The results showed that the precipitation of MnS inclusion would influence the concentrations of solutes Mn and S, leading to the changing of ki. Due to the precipitation of MnS, the kC and kS decreased first and then increased with temperature decreasing, while kSi, kMn, and kP changed monotonously. The impacts of solidification temperature on kSi and kMn were greater than that on kC, kS, and kP. With the increase of S content, kC, kSi, and kP increased while kMn and kS decreased. Whereas, an opposite effect was found with the increase of Mn content. The order of influence extent by S and Mn contents was kSi > kS > kMn > kC > kP.