The quality assurance theory of Dr. Noichi Taguchi, a famous Japanese quality management expert, is self-contained, and its theoretical basis is Taguchi's quality view and quality loss function. It divides product quality control into online quality control and offline quality control. Off-line quality control is to design product quality by three-time design method. On-line quality control focuses on controlling product quality in manufacturing process, which is divided into process diagnosis and adjustment, prediction and correction, inspection and treatment. In Taguchi's theoretical system. The core is to closely link quality with economy and express it with quality function. Therefore, the quality loss function is an important content of Taguchi's quality theory. He pointed out that the quality of products is related to the social losses caused by listing, and that the size of social losses directly reflects the quality. Therefore, products that are qualified and cause little loss to society after listing are of high quality.

Noichi Taguchi believes that the quality of a product cannot be judged simply by whether it meets the tolerance. Tolerance is only the criterion of decision-making, and does not represent the inherent quality of products, which is mainly determined by the deviation between quality characteristics and design center system.