We have developed a method to solve X-ray spectra. The method includes a iterative with range limit and a periodic smoothing. Better resuts had been obtained by use the method to solve X-ray spectra in laser nuclear fusion. This paper places stress on introduction the smoothing technique in the method. A smoothing weigh fuction was formed and iterative spectra was treated periodically by the weigh fuction in iterative Course. Computational results show, Numerical structure producted in iterative course of X-ray spectra was eliminated and convergence of iterative was improved and level of solving spectra was raised by using the techn-ique. physics bases of smoothing are discussed, a theoretical analyses about smoothing and experiemental results on number of smoothing and weigh fuction are given in this Paper.