Multi-keV X-rays are used as backlighting sources of the radiography to diagnose plasmas in high energy density physics (HEDP) experiments. We study the characteristics of Ti-4.7 keV and Cl-2.7 keV X-rays driven by nanosecond laser at the SG-II laser facility. The results show that the X-rays from Cl plasma are primarily He-like and H-like line radiation, with 2.7 keV He-α line on the strongest line emission. In addition, the relative intensity of Cl X-rays is more than an order of magnitude compared to that of Ti X-rays under the current SG-II laser conditions. Therefore, the Cl X-rays can be used as the backlighting diagnosis.