The invention discloses an optical design method of a light guide plate. The method comprises the steps of three-dimensional modeling, dot designing, simulating and analyzing, index simulating, debugging and optimizing, result outputting, and light guide plate machining. According to the optical design method of the light guide plate, the density, the size and the microscopic-carving scale (V-cut)of diffusion dots on the light guide plate are designed. Meanwhile, the method is matched with the mold designing and machining technology, so that the uniformity and the high brightness of the emergent light intensity of the light guide plate are achieved. According to the invention, the design sequence of the optical design method of the light guide plate sequentially comprises the steps of three-dimensional modeling, dot designing, simulating and analyzing, index simulating, debugging and optimizing, result outputting, and light guide plate machining. According to the appearance, size andsimulation indexes of the light guide plate, the analog simulation design of the light guide plate is realized. Based on the analog simulation method, the optical design and the development process ofthe light guide plate are optimized, and the optical development period of the light guide plate is shortened. The design and development cost of the light guide plate is reduced. The light guide plate is excellent in various performance indexes, short in machining period and high in efficiency.