Objective To explore the application of evaluation of measurement uncertainty in routine coagulation assays based on the data of internal quality control (IQC) and results of external quality assessment (EQA) .Methods Data of clinical coagulation assays of clinical laboratory of Xiangyang city hospital were collected ,Which came from six months of IQC and 3 times of EQA of ministry of health clinical laboratory center from 2012 to 2013 .The combined and expanded uncertainties of 3 measurements(PT , APTT and Fbg) were evaluated according to CNAS top-downapproach .Results When PT were in 12 .72 s and 21 .04 s ,its ex-panded uncertainty were 1 .06 s and 1 .96 s ,and APTT in 36 .6 s and 50 .6 s were 2 .59 s and 5 .30 s ,and Fbg in 3 .32 g/L was 0 .30 g/L .Conclusion Evaluation of measurement uncertainty by using internal quality control data and EQA results for routine coagula-tion detection index is economical and practical and acceptable way ,with good clinical practice .