Forming simulation has been carried out for prediction of forming limits. Work-hardening curve is deeply involved in the reliability of the forming simulation. Measurement method of large strain region has not been established. In this paper, a new method of determining work-hardening curve of large strain region is proposed. The proposed method consists of compression test and optimization scheme. In the optimization, using the least-square method, the work-hardening curve is determined from the relationship of load and displacement obtained by the compression test and finite element analysis. Jigs are designed to eliminate the effects of friction by constraining the slip between a specimen and jigs. Dumbbell-shaped specimens are designed to prevent re-contact with the jigs. In the experiment, low carbon steel was used as specimens. The proposed method was carried out and the work-hardening curve of large strain region was obtained.