In this paper the surface viseosity of BF slags bearing high titania has been mea-sured by an experimental device called LASVIM(Laser Surface Viscositymeter)which is designedby authors,and the comparision of the results with the previous works of the authors shows that thesurface visccoity of BF slag containning high titania is depending on its foaming property, Severalfactors on the surface viscosity are also investigated.