Non-destructive testing of a material′s mechanical properties has been a prominent topic in recent years. In this paper, a new non-destructive testing method is investigated. Two types of tests used for measuring mechanical properties of materials (continuous ball indentation tests and conventional tensile tests) are discussed and applied to measure the yield strength and tensile strength of three kinds of pressure vessel steels used in China, including 15CrMoR, Q245R, and Q345R. Comparative analysis shows that the measurements done by the continuous ball indentation test are feasible and more accurate. This proves that the continuous ball indentation testing method can be applied to the non-destructive testing of mechanical properties of some engineering materials.