A method to eliminate the damage aroused by intrinsic prepulse of Blumlein transmission line is proposed. It is used as the forming line in the experiment of capillary discharge soft-X-ray laser,and an additional prepulse is loaded successfully. Ne-like Ar 46.9 nm soft-X-ray laser whose spectra detected by a Rowland spectrograph is obtained. We also detected the directionality,divergence and the gain characteristics of Ne-like Ar 46.9 nm soft-X-ray laser. With the help of Blumlein transmission line,the service efficiency of Marx generator is increased,which is helpful to achieving miniaturization of capillary discharge soft-X-ray. Finally,the supposed applications of 46.9 nm soft-X-ray are also discussed in this paper.