Abstract: In order to obtain the demands of parts with high quality, lightweight and less cost, hydroforming, as an important metal forming process, is developed fast. Because the liquid is used as the pressure transfer medium, the process parameters can be controlled precisely by online real-time controlling the liquid. And also, the need of forming dies can be reduced. However, It restricts the use of hydroforming process that the heavy hydroforming press is required. It is proven that the forming load for hydroforming equals the liquid pressure times projection area along the pressure action direction, and it is irrelevant with punch shape. There are three ways of less-loading hydroforming：Decreasing the projection area, decreasing the material flow stress and adopting appropriate preform. It is also indicated the concrete less-loading method for dieless hydro-bulging spherical vessels, for hydro-bulging protective ring and internal high pressure forming. Some practical application of less loading hydroforming is given too.

Key words: Hydro-bulging, Less-loading forming, Spherical vessel, Tube hydroforming