Abstract: By using the dimensional analysis and finite element computations, the frictional effects on spherical indentation of strain hardening solids to exact the plastic properties of material are examined. By defining a representative strain dependent on the energy, based on the representative strains and representative stresses corresponding to two different indentation depth, the plastic properties of materials are uniquely determined. Then the frictional effects on the indentation response, representative stress and identification of the mechanical properties can be obtained. It is shown that the effect of friction on the indentation is closely related to the strain hardening exponent, the ratio of the elastic modulus to yield stress and the ratio of the reversible work to the total work done by the indenter. The bigger the ratio of the reversible work to the total work is, the smaller the effect of friction is. The effect of friction on extracting the mechanical properties cannot be ignored. While the friction coefficient is unknown, for the materials with the bigger ratio of the reversible work to the total work, the reasonable result can be obtained using the coefficient taken as 0.15 to extract mechanical properties.