The research of carbon content along the casting direction of 82B cord steel billets is of great significance for improving the quality of cord products from subsequent processing. However, the traditional segregation and billets quality evaluation methods have certain limitations, such as sampling length and analysis area, which affect the accuracy of quality judgment. Thus, the statistics of extreme values (SEV) was introduced to predict the maximum value of carbon element content along the casting direction, which can quantitatively characterize the segregation degree. The size of the selected billet is 150 mm × 150 mm, and the sampling location is the centerline of the billet. The experiment was conducted by considering the effect of cooling intensity and casting speed on the maximum value of carbon element content. Firstly, the calculation results show that the SEV method can predict the maximum value of carbon element content along the casting direction of 82B cord steel, and the SEV method is proved to be effective by analyzing the carbon distribution and fluctuation in billets. To some extent, the SEV method can break the limitations of the sampling length and analysis area by predicting the maximum value of carbon element on a larger range of continuous casting billets with few samples. During the continuous casting process, the increase in cooling intensity makes the surface shrinking rate increase, which can slow down the flow of solute-enriched liquid to the center, and the center segregation can be reduced. On the other hand, the function area of the final electromagnetic stirring can be expanded with the increase in the casting speed, which can reduce the concentration of carbon element in the center of the billets and reduce the maximum value of carbon element content. It can provide a new theoretical reference for the quantitative calculation of carbon content in continuous casting billets and the quality evaluation of continuous casting billets.