PT. Rukun Citra Abadi is a manufacturing company that produces cartons in Indonesia.This is a new company that is still under development, especially the quality control system, as seen from the defective products produced. To overcome this problem, there will be applied the Six Sigma method. The data collection and processing phase starts from define, which is an analysis of product quality characteristics or Critical to Quality, then measure at the stage where DPU, DPMO and conversion values are calculated sigma value, then continued to analyze stage the analysis carried out based on the results of the quality characteristics (CTQ) which has been determined at the define stage with the sequence method Defect Concentration Diagram, Fish Bone Diagram and Failure Mode and Effect Analysis (FMEA). The results of the analysis obtained DPMO values in January (9550), February (8886) and March (7025), after the implementation of the DPMO value in April (5086) and sigma values from January to March, 3.84; 3.87 and 3.95 in April (4.06). The cardboard box DPMO value in January 6530, February (6560) and March (6965), after the implementation of the DPMO value in April (6071) and the sigma value from January to March, 3.99; 3.99 and 3.95 in April (4.02). The sigma value for sheet and cardboard box cartons has increased, which means that the implementation has succeeded, in other words has succeeded in reducing defective products in the production process of cardboard.