In order to improve the testing accuracy for the steel bar position,Measurement Systems Analysis (MSA) technique is used to systematically test the discrimination,bias,linearity,repeatability,reproducibility and other indexes for the TCC determinator.After analysis,we found the source of the determinator variation,and figured out that determinator had linear bias and data correction was necessary during the process.The determinator can be used to judge if the thickness of concrete cover is qualified or not and make a rough estimate for the process capability index during the construction process.?