Extreme ultraviolet lithography (EUVL) technology that harnesses extreme ultraviolet (EUV) source with wavelength of 13.5 nm can easily break through the technology node of 30 nm thus realize large-scale industrial production. Capillary discharge that directly converts electric power into EUV radiation power of the plasma has a higher conversion efficiency of energy. A coupled EUV source from three plasmas in capillary discharge, by making use of the interaction of the thermal expansion of laser produced plasma (LPP) with the Lorentz force received by three plasmas, produces a larger area of EUV radiation. Therefore, it greatly reduces the repetition rate of capillary discharge under the premise of the requirement for EUV utilization which is favorable for lithography production. On the basis of realizing concurrent discharge of three pairs of electrode and synchronized ignition of discharge with laser, the effect of laser on the coupled source is discussed. It is found from experiment that the positional coupling has so little influence on EUV source that the dynamical coupling caused by LPP becomes the key to the problem to be solved gradually.