In this paper, a new forming process of the large-size forgings within the limit of forming loads is developed by introducing the incremental forging method and combined forming method. For the development of the forming process, various related processes are proposed and modelling experiments of plasticine and corresponding numerical simulation ate carried out. Thus, an optimal process considering the productivity and economical efficiency is recommended from the study of formability and forming loads, etc. The selected process is subjected to a modelling experiment of lead and 1/7 scale prototype experiment of the real material so as to verify the effectiveness of a selected process as well as to determine the design parameters. The developed process is then applied the forging product of dome shape. Dome-shaped forgings can be produced by the developed process within the limit loads and with the simple tools.