Abstract: Objective To evaluate the results of the external quality assessment (EQA) on the laboratory diagnosis of Anaplasmosis and differential diagnosis between Anaplasma and other rickettsiae in 10 provincial/municipal CDCs laboratories in China. Methods The micro-indirect immunofluoresce assay (mIFA) recommended by WHO Rickettsial Diseases Collaborating Center was adopted as a standard serological diagnosis technique. The performances of two nested PCR assays, one testing for most members of family Rickettsia to amplify groEL gene and other targeting members of family Anaplasma to amplify 16S rRNA gene were evaluated. The laboratories involved received a package containing primers and reference templates(P1,P2,P3,P4,P5)for PCR tests and S1 and S2 reference sera for serological assays. Each laboratory was required to perform these procedures based on its own laboratory condition including equipments and some reagents except the reference materials provided. Results Seven laboratories from the 10 CDCs reported the results for testing S1 and S2 references, and the results in 5 of them (71.4%) were qualified according to the assessment criteria. Eight laboratories reported PCR results, but the significant differences on specificity and sensitivity of PCR between them were found, 62.5% (5/8) of laboratories provided acceptable results for P2 and P3 references and 50% (4/8) of laboratories provided acceptable results for P4,P5,P6 references. For repeatability evaluation,all the laboratories reported acceptable results according to the statistical procedures described. Conclusion This EQA demonstrated all the laboratory involved had systematic errors in their performances. It is necessary for these laboratories to improve their test condition, strengthen the internal quality control and take part in the external quality control activity regularly to improve the diseases diagnosis and differential diagnosis capacity.