From the diet-insect- insecticide's relation, the influence of diets on the larvas of cigarette beetles was investigated. The diets included liquorice, kernel and flue-cured tobacco. The results showed that the diets could apparently change the susceptivity of larvas of cigarette beetles to insecticides, and the larvas fed with kernel featured the strongest resistance, and the larvas fed with liquorice showed the weakest resistance. The diets also had a evident effect on abundance of yeast-like symbionts (YLS) in the body of 5th instar larvas. The larvas fed with kernel had more YLS than the others. Besides, the diets also affected the activity of detoxifying enzymes ( CarE and GSTs) of larvas.