Large　dendritic　MnS　is　usually　formed　in　high　sulfur　steels　and　detrimental　to　the　transverse　impact　property　and　mechanical　property　of　steels.　In　order　to　accurately　reveal　the　effect　of　cooling　rate　on　the　precipitation　behavior　of　MnS　in　high　sulfur　steels,　directional　solidification　experiments　under　different　cooling　rates　were　carried　out.　After　directional　solidification,　precipitated　MnS　inclusions　were　mainly　type　II　and　distributed　between　dendrite　arms.　The　size　of　MnS　increased　with　the　increase　of　solidification　distance.　With　the　increase　of　cooling　rate　from　0.18　to　0.87　°C/s,　the　number　density　of　＞　5　μm　MnS　gradually　decreased　from　55　to　41　pct,　while　the　number　density　of　3　to　5　μm　MnS　increased.　Meanwhile,　the　solidification　structure　of　steel　changed　along　the　path　of　planar　crystal　→　cellular　crystal　→　dendritic　crystal.　The　relationship　between　the　cooling　rate　(R　c)　and　the　primary　dendrite　arm　spacing　(λ)　for　high　sulfur　steel　could　be　expressed　as　λ=251.63Rc-0.275　based　on　the　experimental　result.　A　faster　cooling　rate　suppressed　the　macro-segregation　of　Mn　and　S,　and　the　micro-segregation　of　Mn　was　more　severe　than　that　of　S.　Thermodynamic　calculations　indicated　that　the　MnS　could　precipitate　when　the　solid　fraction　of　steel　was　greater　than　0.82　within　the　current　cooling　rate　range.　©　2023,　The　Minerals,　Metals　&　Materials　Society　and　ASM　International.