High flux, Multi-keV X-rays, can be efficiently produced from nano-second laser interaction with metal target. Multi-keV backlight X-ray source is very important in inertial confinement fusion and high-energy density physics research. The one-dimensional numerical simulation results propose a laser plasmas radiation model, and the model is compared well with Shenguang II experimental results. The pinhole-assisted point-projection (PAPP) backlight is improved by the model; the rear-on PAPP backlight for low-Z metal target and the side-on PAPP backlight for middle-Z metal target are developed. The experiment is performed on Shenguang II 9th laser facility. The static stream line obtained with novel PAPP backlight provides high-quality capsule image, and the spatial resolution is better than 10 μm. Results show that novel PAPP backlight has advantages of traditional PAPP in source brightness, spatial resolution and image contrast.