Abstract: From 2010 to 2020, a total of 119 labs, excluding labs from Hong Kong, Macao, and Taiwan regions, had participated 5 proficiency tests of seawater salinity using 7 set samples. In the testing 443 seawater salinity test data had been obtained. Since each group of data obviously deviates from the normal distribution, algorithm A was adopt for evaluating the results of proficiency testing of seawater salinity other than classical statistical and standardized interquartile distance methods. Results showed that from 2010 to 2020, the dissatisfaction rate decreased from 20.3% to 4.9%. Laboratories that participated the tests more frequently or with CMA qualification had less dissatisfaction result. Thus, proficiency testing was an effective means to improve the abilities of laboratory testing technology and CMA quality management system plays an obvious role in ensuring the accuracy of test data.