According to the light distribution of LED, we figure out the formula of a dot illuminance on the plane of the edge-lighting backlight light guide plate (LGP), and an arrangement formula of scattering dots in the LGP as well. The main purpose of this paper is, by studying the shape of the scattering dots in the LGP, to find out the scattering dots shape which is the most suitable for the LGP. Based on the hemispherical dots shape, according to principle that the light coupled into the LGP in two directions is reflected by the hemispherical scattering dots and just outputs from the LGP, it is obtained that the optimum shape of scattering netted dots is the cone whose apex angle between 90° and 132.2°. Under the condition of a certain uniformity of output light flux, by means of TracePro software simulation, the total output light flux is compared for the LGP with different apex angles of cone scattering dots. The experimental and theoretical results match well with each other.