Abstract: Compared with the traditional mechanical testing method requiring samples of specific shape and size, indentation method has the advantages of simple manufacturing of samples and in-situ testing. The existing indentation characterization methods mainly relies on indentation load–depth curve, while the residual indentation morphology is an intuitive response to material plastic mechanical properties. Effective acquisition of metal plastic parameters by residual indentation morphology can provide a new characterization method for metal plastic mechanical properties. In this study, spherical indentation tests of Cu/Mg have been carried out by the Instron universal material testing machine, the residual indentation morphology of Cu/Mg was scanned by the contour morphology system and the obtained morphology feature will be used as the data basis for subsequent studies. The comparison result of residual indentation morphology from indentation numerical simulation and experimental test was taken as the goodness of fit. In order to discard the data less than zero, determine the initial value range of the optimization parameters and improve the efficiency of optimization calculation, related improvements of parameter screening, preprocessing, repeatability judgment and convergence conditions were carried out on the traditional Nelder-Mead algorithm. Based on the secondary development of Abaqus software and the improved Nelder-Mead algorithm, the optimization process was performed to obtain the plastic mechanical parameters of Cu/Mg. Also, the related plastic mechanical parameters of Cu/Mg was acquired through the conventional uniaxial tensile test and characterization based on the Instron universal material testing machine. By comparing the optimization results from algorithm and the tensile test characterization results, the relative errors of related plastic mechanical parameters of Cu/Mg obtained from optimization algorithm were identified, and the effectiveness of the proposed method for obtaining metal plastic parameters based on optimization algorithm and residual indentation morphology was verified. Relevant research provides a new and effective method for characterizing the mechanical properties parameter of metals.