Abstract: Such as whether the data shall be rounding or not,how to round them,will directly affect test results in compliance with technical specification. Considering the importance of data rounding,the conditions and methods of data rounding in several common international standards(e.g. ASTM(ASME) and RCC-M and ISO) were introduced. Finally,taking tensile test for instance,issues of its data rounding were discussed. The conclusion of the instance was the data should not be rounding and the test result was incompetent.