Abstract: In the process of yield strength measurement via the tensile test,if the center line of the specimen is not in light with the loading force axis of the testing machine,the tensile specimen will be subjected to a horizontal shear force that will affect the deformation amount of the specimen as measured with the extensometer,resulting in the irregular linear elastic section of the stress-strain curve that will in turn affect the accuracy of the yield strength test. The yield strength test is conducted with the specimens in six different high,medium and low steel grades as selected and clamped in different positions and with different methods. The test result shows that the yield strengths of the specimens as measured are quite different to each other,and that the higher the steel grade is,the influence on the strength as tested is more significant,which leads to such a conclusion that the clamping position of the specimen can seriously affects the result of the yield strength test.