Abstract: This experiment was conducted observe,through electron microscopy,the struc-tural changes in the integument and mid-gut of the silk worm fed with fluoride.The resultsshowed various degrees of damage in the integument and mid-gut.Vacuoles appeared inthe epithlium of the integument and precipitates appeared in the outer epidermis in some se-vere cases.The pathological changes in the mid-gut were more obvious:the structure of thecell layer became loosened,the cell vacuolated,the mitochondria void,the endoplasmicreticulum swollen,the nuclear membrane degenerated and the nucleoplasm agglomerated.The mechanism of the fluoride poisoning to the silk worm was discussed in relation to pro-viding scientific basis for the control of air pollution in sericulture production.