Objective To investigate and analyze the preventive effect of boron on the cartilage damage in rats with intake excessive fluoride. Methods Fifty-ix Sprague-Dawley rats were divided into the control group (C, intake distilled water), the excessive fluoride dose group (EF, intake distilled water with 100ppm F -) and the boron prevention group (P, intake distilled water with 100ppm F - as well as the supplemental boron dietary). 3 to 5 months later, fluorine contents in serum, RNA contents in costal cartilage were assayed. The morphological changes in tibia growth plate cartilage (GPC) in rats were observed. Results Although exposed to the same dose of fluoride, the fluorine contents in serum in rats of P group decreased notably compared with those of EF group, the damage of tibia GPC under optical and electron microscope lessened significantly, and RNA contents in costal cartilage increased obviously in the 3 rd month. Conclusion Boron added could decrease the fluorine level in the body and relieve the toxic symptom of excess fluoride, and thus boron has a preventive effect on skeletal fluorosis. Objective To investigate and analyze the preventive effect of boron on the cartilage damage in rats with intake excessive fluoride. Methods Fifty-ix Sprague-Dawley rats were divided into control groups (C, intake distilled water), the excessive fluoride dose group , intake distilled water with 100ppm F -) and the boron prevention group (P, intake distilled water with 100ppm F - as well as the supplemental boron dietary). 3 to 5 months later, Results cost of cartilage were assayed. The morphological changes in tibia growth plate cartilage (GPC) in rats were observed. Results Although exposed to the same dose of fluoride, the content of in serum in rats of P group decreased notably compared with those of EF group , the damage of tibia GPC under optical and electron microscope lessened significantly, and RNA contents in costal cartilage increased obviously in 3 rd month. Conclusion Boron added could decrease the fluorine level in th e body and relieve the toxic symptom of excess fluoride, and thus boron has a preventive effect on skeletal fluorosis.