Abstract: About 33% of the discarded tobacco leaves are unused and become waste during processing, which not only pollutes the environment, but also wastes resources. This study attempted to extract and purify plant secondary metabolites, such as nicotine, from discarded tobacco leaves by using biotech. These extracts could be used as raw material in chemical industry to develop products, such as medicine, biological insecticides, feed for mushroom, and fertilizers. Through culture and pot experiments, it was found that nicotine could inhibit the growth and proliferate of microbes, whip in and kill plant aphides efficiently. And there were a lot of amino acids in the rest of fermentation treated tobacco waste leaves. Our research indicated that to gain the recycle utilization goal, the waste tobacco leaves could be used as raw materials not only to produce bio-insecticides and bioorganic fertilizers, but also to raise edible fungus after detoxification process.