Quality assurance is divided into internal quality assurance and external quality assurance, internal quality assurance is a means of enterprise management, the purpose is to obtain the trust of business leaders. External quality assurance is in the contract environment, supply-side gain the trust of the trust as a means of demand-side. Dimension, quality assurance, content, and not simply to ensure quality, but more important to those affected by the quality of the quality system elements of a series of planned and organized the evaluation activities, in order to achieve business leaders and the demand side of the trust to provide sufficient and reliable evidence.