The microstructure of experimental nickel-base single crystal superalloys with different levels of carbon has been studied.The results indicated that with increasing carbon addition,the liquidus temperature decreased obviously and the as-cast microstructures exhibited a decrease in the amount of γ/γ eutectic structure and an increase in the volume fraction of carbides.The carbides formed in these alloys were most script-type MC carbides which appeared continuous dendritic networks in the interdendritic region.The segregation behavior of element W was influenced by the carbon addition.