Carbon macrosegregation in continuous casting strands originates from the uneven distribution of carbon between the solid and liquid phases during solidification. The initially solidified solid phase （dendrites） has a lower carbon content， causing excess carbon to enrich the liquid phase at the solid-liquid interface front and form localized high-carbon zones. This defect persists throughout the entire process from hot rolling to product service， severely deteriorating material processability， inducing banded structures and heat treatment defects， and significantly reducing the mechanical properties and service life of the final product. This study systematically investigates the carbon macrosegregation behavior of low-carbon alloy steels （20CrMo， 3130）， medium-carbon alloy steels （4142， 45）， and high-carbon alloy steel （GCr15） under different continuous casting process parameters （superheat， casting speed， mold electromagnetic stirring （M-EMS）. The research defines optimized process windows for typical steel grades： for low-carbon steel 20CrMo， a superheat of 20 ℃–25 ℃， casting speed ≤1.60 m/min， and M-EMS current of 195A–205 A are recommended； for medium-carbon steel 4142SR， a superheat of 20 ℃–28 ℃， casting speed of 1.58m/min–1.62 m/min， and M-EMS current of 200A–208 A are recommended； for high-carbon steel GCr15， a superheat of 18 ℃–25 ℃， casting speed ≤1.16 m/min， and M-EMS current of 195A–202 A are recommended. The main results are as follows： 1） Effect of carbon content： As the carbon content of the steel grade increases， the proportion of negative segregation from the strand center to the 1/2 radius region decreases from 45% to 28%， and the inner arc/outer arc negative segregation ratio decreases from 1.5 to 1.24. 2） Effect of superheat： With constant casting speed and electromagnetic stirring intensity， the tundish superheat within the range of 20 ℃–30 ℃ yields the optimal （lowest） carbon segregation index. 3） Effect of electromagnetic stirring： Within a specific magnetic field intensity range， enhancing M-EMS effectively reduces the fluctuation range of the carbon segregation index. 4） Effect of casting speed： Increasing the casting speed leads to a significant rise in the carbon segregation index of the strand. This study quantitatively reveals the influence of key continuous casting parameters on carbon macrosegregation in alloy steels with different carbon contents. It provides a direct basis for effectively controlling carbon macrosegregation in industrial production by optimizing parameters such as superheat， electromagnetic stirring intensity， and casting speed， with particular emphasis on the need for targeted process optimization based on the steel grade's carbon content.