Abstract: Coupling the radiation transport equations of X-ray laser and rate equations,we study gain saturation process of several X-ray lasers in Ne-like Ge plasma and compared simulated results with calculation of the usual saturation equation. The great differences have been found in deep saturation stage. Simulated re- sults also show the “burning hole” in gain curves and the line width decreasing and increasing with increas ing length before saturation and after that.