The definition of best average netted dot density(BANDD)is proposed based on the research of the pattern of the netted dot for light guide plate(LGP), in order to elaborate the optimal design for the netted dot of LGP. A backlight module(BLM) is modeled in the light simulation software based on the theory of LGP guiding light, a group of differently uniform netted dot density (NDD) are applied in the model to test the effect on performance, the results indicate that the NDD from 0.1 to 0.4 relatively balances efficiency and uniformity. Further more the layout of the netted dot in the scale mentioned above is optimized to improve the uniformity; the results of simulation state clearly with the NDD from 0.2 to 0.35 can reach the requirement of uniformity in development stage. The corresponding experimental samples are made; the result of the experiment demonstrations that the BANDD is located in 0.25, it agrees well with the theoretical predictions. It has certain guiding significance that the conclusion of the study are applied in the actual development, and will accelerate the procedure of BLM and reduce the counts of designing editions, and cost down the development expense of the BLM.