This paper summarized and analyzed the relevant literatures of ancient medical books and recent clinical and experimental studies on acupuncture needle retaining time,and found that the length of retaining needle time played a direct and important role in acupuncture effects. There was optimal needle retaining time in the treatment. Physicians in past dynasties took the retaining needle seriously and modern research also confirmed and developed the ancient understanding of retaining needle in a certain extent. But the concrete retention time is still not consistent in the current study. In the future standardized scientific research work should be carried out to seek the best needle retaining time with high recognition and objectivity. Based on the disease,it should take into account the differences on illness,time,individual,meridian and points to determine needle retention time