Abstract: Heavy rail steels,PD2 and PD3,are chosen for the investigation of the impact tougness in as-rolled and reheated state.The results show that the condition of austenite(austenite grain size,homogeneity of chemical contents as well as dissolution and precipitation of carbides),the morphorlogy of pearlite and the interlamellar spacing are the three main structure factors influencing the toughness of pearlite.A basic plan for the toughening of pearlite rail steels is presented,which includes refinement of austenite grain and pearlite interlamellar spacing,homogenization of austenite content and complete dissolution of strong carbide forming elements in the austenite.