Abstract: By means of OPM, SCM, EP and chemical analysis, the role of RE in centrifugal-casting grey cast iron pipes is studied. The results show that the structures are rery course and heterogeneous in glay cast iron pipes for ordinary centrifugal-casting. When a suitable quantity of RE is added into the melt during pouring, both the macro-and microstructures become fine and homo-geneous,and the degree of chemical segregation is also considerably reduced.