Extreme ultraviolet lithography (EUVL) technology, the extensional technology of 193 nm immersion lithography, would breakthrough the 30 nm node or below and become the main technology of the next generation lithography (NGL). Although the capillary discharge extreme ultraviolet (EUV) source could provide efficient and convenient light for EUVL investigation, its low power confines the development of EUVL. The concept design of three-line capillary discharge EUV source will be essentially different from conventional capillary discharge channel, which will also make a great difference of dynamical mechanism. The circular loop band plasma column of three-line capillary discharge EUV source irradiates more EUV power than conventional capillary discharge device does and the optimal divergence angle of the former will be improved too. The concept design plan of three-line capillary discharge will not only create a new area for EUVL research technically, but also help to produce light sources industrially and economically.