Abstract: Comparatively analyzed here in the article is the chemical compositions of the while band area and the nearby matrix of the Cr-Mn-Mo low alloy steel CC billet.And also tested are the microstructure and the mechanical properties of the as-quenched and the as-quenched and tempered Cr-Mn-Mo low alloy steel pipes to study the effect by the white band on the mechanical properties of the said steel.The result shows that the chemical composition of the white band in the CC billet presents negative segregation;after being quenched, the hardness of the white band area is significantly different from that of the matrix, and there also is some difference between the microstructures of the two.After being quenched and tempered, there is no obvious difference between the microstructure of the white band area and that of the matrix, the hardness difference between the two is tremendously reduced, and the strength and impact toughness difference are so little.Therefore it is concluded that the above mentioned white band has very slight effect on the overall performance on the Cr-Mn-Mo low alloy as-quenched and tempered.