This study organizes and analyzes early iron-production techniques developed in Chungju, the center of iron production in ancient Korea. Direct smelting produced impure iron from iron ore and was the main technique in Chungju in ancient times. This is backed up by tap slag found in large quantities at many ruin sites. Furnace structure and tuyeres were analyzed along with smithing techniques confirmed in the iron production ruins. This has produced an interpretation of overall iron production techniques.