Abstract: According to GB/T 231.1-2010 Metallic Materials-Brinell Hardness Test-Part1:Test Method, Brinell hardness test (HBW10/3 000) was done to flat-rolled steel sheets, and the measurement uncertainty of the test results was evaluated and summarized. The results show that when the coverage factor k=2 and adopting the method of considering the hardness tester maximum allowable error, the measurement uncertainty of Brinell hardness test was as follows:(323±9) HBW10/3 000; when adopting the method of considering the hardness tester system error, the measurement uncertainty of Brinell hardness test was as follows:(323±6) HBW10/3 000. The difference between these two evaluating results was related to the size of uncertainty source. In daily use, the Brinell hardness testers should be verified and calibrated regularly to ensure that all parts of the hardness tester are working properly within the national standard.