The controllable parameters of shape and size of the scattering points of the plastic optical fiber (POF) core are of great significance to the design of the LCD backlight based on the semiconductor laser diode (LD) and the side-glowing POF. A laser marking method for POF core scattering points with surface damage free was researched. Based on the principle of edge-ray in non-imaging optical theories, the secondary focusing at laser beam for marking POF core scattering points was analyzed, and the formulas for focal point coordinates of laser incident on the POF was derived. The effects of focusing lens height, laser power and marking repeat times on the shape and size of scattering points in the fiber core of POF were studied experimentally by using a 1.06 滋m laser marking system. Relative intensity distribution of the scattered laser at 650 nm was used to detect scattering points in fiber core, the shape and size of the scattering points are judged by comparison of their micrographs . The experimental results showed that the shape of scattering points in the fiber core was determined by focusing lens height.When the focusing lens height was the focal length of the lens, elongate scattering points along the radial direction can be obtained. With the increase of laser power or marking repeat times, the size of scattering points increased. The laser damage threshold of POF was about 80 W/mm2 under single laser marking. However, the laser power density should be greater than 140 W/mm2 in order to make the scattering points have steady elongated shapes .