6 Sigma is an effective method of process quantization, control and improvement. In consideration of problems which could consist in quality management or process control of agile software development method, the paper analyzes feasibility of 6 Sigma in agile software development method, sets YfX black-box model, white-box model and mathematical model based on 6 Sigma, and analyzes DMAIC process, continual improving the Agile software development process.