By using the technique of oscillation-amplification the small signal gain characteristics of an X-ray preionized discharge XeCl laser at a gas pressure of up to 10 atm have been investigated. The experimental result shows that for a Xe:HCl=10:l mixture with different amounts of neon dilution; the total gas pressure Pmax corresponding to the peak small signal gain appears to increase monotonically with the increasing amount of neon dilution, but the absolute partial pressure of HC1 corresponding to Pmax at various mole ratio, however, seems to remain relatively constant.