Using the finite element analysis, the deep indentation of strain-hardening elastoplastic materials by a rigid, spherical indenter has been studied. The simulation results clearly show that the ratio of the indentation load to the maximum indentation depth increases with the increase of the strain-hardening index and reaches a maximum value at the maximum indentation depth being about 10% of the indenter radius. The power law relation between the indentation load and the indentation depth for shallow indentation becomes invalid for deep indentation. However, the ratio of the plastic energy to the total mechanical work is a linear function of the ratio of the residual indentation depth to the maximum indentation depth, independent of the strain-hardening index and the indentation depth.