Six Sigma is a popular approach to drive out variability from processes using powerful statistical tools and technique. Six Sigma permits only 3.4 defects per million opportunities. Six Sigma follows basics methodology to improve existing process, i.e. DMAIC. Define, Measure, Analyze, Improve, Control. It is , scientific, systematic and fact based approach. This paper also includes various applications of DMAIC methodology in different business sector like Electronics sector, Chemical and Agriculture manufacturing sector etc.