The service industry plays an important role to the development of Indonesian economy. Recently, the fast food industry has a good growth due to customers preferences. This significant contribution and industrial growth are not accompanied by the quality of industrial performance. This condition lead to a weak competitiveness, especially to face of the ASEAN Economic Community (AEC). The fast food industry needs to develop a specific strategy to improve the service system. This study uses a lean approach to improve the service system in a fast food restaurant. The method used is the integration between six sigma and TRIZ (Theory of Inventive Problem Solving) to get a creative problem-solving innovation in improving service industry performance. Based on the research conducted, it can be identified that the waste occurs in fast food industry is the service delay due to the process of giving flavor with a total time of 527 seconds. Improvement strategy to reduce the waste is to change the process of giving flavor (parameter changes) and implementation of 5S in the work area (enriched atmosphere). There is a time improvement of 90% by implementing the strategies that have been obtained.