Abstract: The hot ductility of Nb-Ti containing X-52 steel cc slab has been examined over the temperature range from the melting point to 700 ℃.The loss of hot ductility was analyzed according to the charateristics of fractures and precipitates. It was found that there exist two low ductility temperature regions within the tested temperature range, that is, Region Ⅰ from the melting point to 1380℃ and Region Ⅲ from 925-825℃. In region Ⅲ, the ductility loss is due to the dynamic precipitation of fine partiocles of NbCN at the austenite grain boundaries. The good effect of titanium on hot ductility is attributed to titanium reducing precipitation of the more detrimental NbCN and preventing the formation of ferrite films around the austenite grain boundaries.