PDCA cycle theory and methods are not only for quality management, but also apply to business management in all its aspects. It is divided into the management of the circulation process, each cycle of the process to solve one or two problems. Through the cycle constantly improve the quality of their work to promote the standardization and management of structured, to reduce blindness and improve scientific level.

Spiral
PDCA cycle is not a simple cycle of operation, but a rising, improve the process. It is like a staircase on wheels in the rotation, rotation every week, on the request further before, to achieve quality objectives, level by level raises. Such a cycle of increased quality problems are resolved, product quality will be steadily increasing.

Small cycle within big cycle
Quality assurance system is a complete system, subsystem relatively independent of the system and subject to greater operational process, each cycle subsystem (small Central), but more controlled system in the cycle (the Central ), to form the " Small cycle within big cycle " model cycle.

Take road transport enterprises quality assurance system as an example, the entire enterprise quality management cycle can be regarded as a big ring; workshop, the quality of the management team can be regarded as business cycle is controlled by the Central small ring; even small transport projects Level, until the team and individuals.

PDCA cycle' s four phases are not completely separate. In practical work plan frequent side, while the implementation of inspection, check-processing, edge-processing program, rather than the rotating machinery.

Small cycle within big cycle is a comprehensive recycling system, the Central linked with the quality indicators. On a cycle of a cycle is the basis for the next cycle is a cycle on a specific content and assurances. Big cycle controls the rotation of small cycle and small cycle promotes the big rotation. Through allocation of different levels to lead the operation of enterprise quality assurance system.