The invention provides a preparation method of high-carbon high-alloy nitrogen-containing billets, comprising the following steps: carrying out pit soaking on a steel ingot and then carrying out blooming cogging; air-cooling the product obtained after blooming cogging to obtain the high-carbon high-alloy nitrogen-containing billet. During blooming cogging, two-fire rolling is adopted: first-fire cogging pass deformation is 5-15 mm; and secondary-fire cogging pass deformation is 15-25 mm. The preparation method of the high-carbon high-alloy nitrogen-containing billets adopts processes of high-temperature soaking, two-fire rolling cogging and spreading air-cooling after rolling. By the adoption of a reasonable heating system, a rolling process and a cooling method and under combined action of the various processes, surface quality of billets can be improved, cogging yield is raised, and requirements on materials for rapid development in the automobile industry are met.