Abstract: The instrumented indentation tests were analyzed by employing dimensional theorem and finite element method. A combined Youngs modulus Ec, defined by Ec=1/(1-ν2)/E+1.32(1-ν2i)/Ei was introduced to accurately reflect the combined elastic effect of an indenter and an indented material, in which Ei and νi were the Youngs modulus and Poissons ratio of the indenter, and E and ν were those of the indented material. Consequently, an approximate relationship between the ratio of Oliver-Pharr hardness HO&P to the combined Youngs modulus Ec and the ratio of unloading work We to total work Wt in indentation was revealed by HO&P/Ec = Γ(We/Wt). Based on the relationship, a new method was then proposed for determining Youngs modulus of materials, and the effectiveness of the method was examined by several experimental examples. The results showed that the test precision of the method was higher than that of Oliver-Pharr method.