The K X-rays emitted from the incident slow highly charged Ar17+ ions are investigated in the interaction with various metal target such as Be, Al, Ni, Mo and Au. The Kβ/Kα ratios and the mean energies of the emitted X-rays are extracted and analyzed from our previous experimental results . It is found that the ratios and the energies are almost independent of the ion velocity and the target element. Meanwhile, a model based on the conductive-electron capture and the cascading de-excitation model is proposed to interpret the experiment. Excellent agreement is found between the theoretical results and the experimental data.