The invention belongs to the technical field of a welding material and particularly relates to a carbon steel covered electrode for the third-generation nuclear power technical welding and a preparation method. The carbon steel covered electrode is characterized by comprising a core wire, a cover and an adhesive, wherein the mass ratio of powder to the covered electrode is (25 to 27):100 and the mass ratio of the powder to the adhesive is 100:(15 to 20). In the welding process of the covered electrode in the invention, electric arcs are stable and splashing is little; slag detachability is good; a postwelding slag crust in the flat welding process can be automatically upwarped; the covered electrode is well formed and has good whole-position operability; after welded deposited metal is subjected to heat preservation for 1h, 16h and 40h at a temperature of 595 to 625 DEG C, mechanical property in the three thermal treatment states meets the technical indexes and has high stability.