Abstract: Objective To investigate the changes of mRNA and protein expressions of osterix(OSX)in the bone of rats with chronic fluorosis. Methods Thirty-six SD rats were randomly divided into three groups(12 in each group with half male and half female):control group,low and high fluoride group.The fluoride groups exposed to sodium fluoride (low:NaF of 5 mg/L and high:NaF of 50 mg/L,respectively)added to the drinking water to produce the animal model of fluorosis.The expressions of OSX protein and OSX mRNA inside the distal femur of the rats with chronic fluorosis were detected by immunohistochemical technique and real-time quantitative PCR,respectively. Results Compared with the control group,mRNA and protein expressions of OSX were increased in low and high fluoride rats,the difference was statistically significant(P<0.05). Conclusion Fluoride might induce the mRNA and protein expressions of OSX,and the change of OSX may be involved in the increase of the bone turnover and be one of the the pathogenetic factors in fluorosis.