Using escape probability method,the effects of radiation trapping on inversion and gain of electron-collisional excitation pumping X-ray laser lines are studied in this paper.As an example,the dependence of the inversion and gain of laser lines at 19.6nm and 23.2nm and 23.6nm in neon-like germanium ion on spatial width of gain region D R and velocity gradient of lasing medium dV/dZ are discussed.