Abstract: Use the methods of metallographic observation, sample-electrolysing, SEM and EPMA, the quantity, dimension, morphologies and composition of non-metallic inclusions in 20CrMnTi steel were investigated.It was suggested that lots of non-metallic inclusions were removed from molten steel during LF refining.The T[O] and [N] contents in slab were 18.53×10^-6 and 46.94×10^-6, respectively, as some air could be inhaled into molten steel.The volume ratio of micro-inclusion in slab was being from 0.085% to 0.11%.The micro-inclusions in molten steel and slab, which were typical production during deoxidization and desulfurization, were comprised with oxide, sulfide, calcium silicates and calcium aluminates inclusions.The quantity of large-scale inclusions in molten steel in tundish and slab were 1.011 mg/kg and 0.785 mg/kg.These typical complex inclusions were silicates and silicate aluminates with higher contents of K₂O and Na₂O, which were the main components in mold powder.