Background: Hemoglobin Alc (HbA1c) measurement is of great value for the diagnosis and monitoring of diabetes. Many manufacturers have developed various experiments to determine the HbAlc concentration. However, the longitudinal use of these tests requires strict quality management. This study aimed to analyze the quality of HbAlc measurement systems in China using six sigma techniques to help improve their performances. Methods: A total of 135 laboratories were involved in this investigation in 2015. Bias values and coefficients of variation were collected from an HbA1 c trueness verification external quality assessment program and an internal quality control program organized by the National Center of Clinical Laboratories in China. The sigma (sigma) values and the quality goal index (QGI) were used to evaluate the performances of different groups, which were divided according to principles and instruments. Results: The majority of participants (88, 65.2%) were scored as "improvement needed (sigma= 6)". Among all the 88 laboratories whose a values were below 3, 52 (59.1%) and 23 (26.1%) laboratories needed to improve measurement precision (QGI1.2), respectively; the remaining laboratories (13, 14.8%) needed to improve both measurement precision and trueness. In addition, 16.1% (5/31) and 15.0% (3/20) of the laboratories in " TOSOH" and "ARKRAY" groups, respectively, were scored as " world class", whereas none of the laboratories in " BIO-RAD" group were scored as " world class". Conclusions: This study indicated that, although participating laboratories were laboratories with better performance in China, the performances were still unsatisfactory. Actions should be taken to improve HbAlc measurement performance before we can include HbAlc assays in diabetes diagnosis in China.