According to the quality problems in one gear enterprise, the DMAIC method which is the core application of the six sigma theory is used to improve the quality of the spiral bevel gear, and the quality data is analyzed by using Minitab software. Firstly, the quality problem is defined in accordance with the DMAIC procedures and the main reasons for quality problems in spiral bevel gears are determined. Secondly, measurement systems and process capability are analyzed. Then, we set a specific program for the improvements for the main causes of quality problems. Through the successful implementation of this project, the quality of spiral bevel gears is greatly improved, and the production cost is greatly reduced. The effect is very significant.