Internal audit is an important means for the laboratory or inspection and testing institutions to evaluate the com-pliance and effectiveness of their own management system,through self-inspection in order to continuously meet the a-greed requirements.Through the implementation of effective internal audit,the laboratory can identify the nonconformity in quality activities,take corrective/corrective measures,promote the continuous improvement of the management sys-tem,and improve the management level of the laboratory.The paper combines many years experience in internal audit of ceramic testing laboratory,systematically analyzes the key links of internal audit work,and discusses how to improve the quality of laboratory internal audit work,so as to provide a basis for effective internal audit.