Objective To analysis the influence factors on the quantitative immunoassays by review and summary of external quality assessment (EQA) results in Jiangsu Province. Methods EQA results were scored by using proficiency testing (PT) method, and analysised with other indicators such as Bias and Standard Deviation Index (SDI). Results The results showed that the average PT score of tumor markers assays was 95 points, the score of endocrine assays was 99 points, it had appeared unqualified cases in three assays. The absolute value of average bias of all the assays was 4%-11%, the absolute value of average SDI was 0.3～1.1 points. Conclusion EQA can be continuous monitoring clinical quantitative immunoassays, and can improve the quality of clinical immunoassays.