In order to meet the requirements of high reliability, long-lifetime and lightweight in a new generation of aerospace, aircraft, high-speed train, and new-energy power equipment, integrated components are urgently needed to replace traditional multi-piece, welded components. The applications of integrated components involve in a series of large-size, complex-shaped, high-performance components made of difficult-to-deform materials, which present a huge challenge for forming ultra-large size integrated components. In this paper, the developments and perspectives of several extreme forming technologies were reviewed, including the sheet hydroforming of ultra-large curved components, die-less hydroforming of ellipsoidal shells, radial-axial ring rolling of rings, in situ manufacturing process of flanges, and local isothermal forging of titanium alloy components. The principle and processes for controlling deformation were briefly illustrated. The forming of typical ultra-large size integrated components and industrial applications were introduced, such as the high strength aluminum alloy, 3 m in diameter, integrated tank dome first formed by using a sheet blank with a same thickness as the final component, and a 16 m diameter, integrated steel ring rolled by using a single billet. The trends for extreme forming of ultra-large size integrated components were also discussed with a goal of providing ideas and fundamental guidance for further development of new forming process for extreme-size integrated components in the future.