Abstract: The influences of iron tailings,basicity,contents of MgO and Al₂O₃ on the viscosity and melting temperature of the blast furnace slag were investigated in adjustment of the slag for preparation of slag wool. The results show that with increase in content of added iron tailing the characteristics of blast furnace slag transforms from short to long feature and the viscosity of the slag changes smoothly. When the addition amount of iron tailings is more than 20%,the viscosity and melting temperature of the slag increase and it is not suitable for direct preparation of slag wool. During the adjusting process for the blast furnace slag with chemical reagent,increasing basicity leads to the further transformation to short feature of slag characteristics and increase in melting temperature which is not benefit for fluidity of the slag.With increase in the content of MgO,both the viscosity and melting temperature of the blast furnace slag firstly decrease and then increase. A better fluidity of the slag can be reached with 8%~10% MgO. Because the content of Al₂O₃ in the slag is relatively small,the viscosity and melting temperature of blast furnace slag change slightly with Al₂O₃ content,which has little influence on the fluidity of the slag.