Objective: To study the effect of fluorine on expression of B-cell lymphorria/leukemia-2 (Bcl-2) and, Bcl-associated x (Bax) protein in rat testis, and to reveal the mechanism of impaired male reproduction caused by endemic fluorosis of coal burning. Methods: Forty male SD rats were randomly divided into 4 groups according to body weight with the method of random digits table: control group, low, moderate and high fluorosis groups. Low, moderate and high fluoride groups were fed, with fluorinated food (20.0, 40.0, 60.0 mg/kg), and control group was fed conventional fat chow (fluorinated 1.3 mg/kg). After 120 and 180 days, the rats were sacrificed. Dental fluorosis was determined by observation and urinary fluoride was detected by fluorine ion-selective electrode. The apoptotic index of spermatogenic cell was measured by terminal deoxynucleotidyl transferase-mediated dUTP. nick end labeling (TUNEL). The expression of Bcl-2 and Bax were measured by immuohistochemistry. Results: At 120 and 180 days, low, moderate and high fluorosis groups were suffered from different degrees of dental fluorosis, the teeth of the control group was normal/At 120: and 180 days, the content of urinary fluoride was increased in turn in the control group, low, moderate and high fluorosis group [(1.69 ± 0.03), (3.56 ± 0.10), (12.09 ± 0.38), (23.55 ± 0.33) mg/L; (1.71. ± 0.09), (4.07 ± 0.25), (16.23 ± 0.28), (8.44 ± 0.50)mg/L; all P < 0.05]. Urinary fluoride of low, moderate and high fluorosis groups at 180 days was higher than that of each corresponding groups at 120 days (all P < 0.05). At 120 and 180 days, the apoptotic indexes were increased in turn in the control group, low, moderate and high fluorosis groups [(0.46 ± 0.11)%, (8.83 ± 1.64%), (17.24 ±3.96)%, (44.21 ±7.85)%; (0.54 ± 0.11)%, (10.41 ± 2.70)%, (22.23 ± 3.96)%, (49162 ± 4.77)%; all P < 0.05]. At 180 days, the apoptotic indexes of low, moderate and high fluorosis groups were higher than those of each corresponding groups at 120 days (all P < 0.05). At 120 and 180 days, the expression of Bcl-2 were descended in turn in the control, low, moderate and high fluorosis groups (0.183 ±0.007, 0.165 ± 0.007, 0.152 ± 0.003, 0143 ± 0.007, 0.184 ± 0:006, 0.159 ± 0.011, 0.151 ± 0.005, 0.135 ± 0.005, all P < 0.05). The expression of Bax of moderate and high fluoride groups (0.194 ± 0.018, 0.209 ± 0.012) were significantly higher than that of the control and low fluorosis group (0.145 ± 0.007, 0.161 ± 0.012) at 120 days (all P < 0.05). The expression of Bax were increased in turn in the control, low, moderate and high fluorosis groups (0.145 ± 0.009, 0.185 ± 0.013, 0.207 ± 0.011, 0.230 ± 0.014, all P < 0.05). At 120 days, the Bcl-2/Bax ratios were descended in turn in the control, low, moderate and high fluorosis groups (1.264 ± 0.044, 1.028 ± 0.096, 0.788 ± 0.060, 0.688 ± 0.064, all P < 0.05). At 180 days, the Bcl-2/Bax ratio of control, low, moderate fluorosis groups (1.277 ± 0.100, 0.865 ± 0.066, 0.731 ± 0.045) was significantly higher than that of high fluorosis group (0.592 ± 0.031, all P < 0.05), and that of control group was significant higher than that of moderate fluorosis group (P < 0.05). Conclusions: Endemic fluorosis of coal burning may leads to increased apoptotic index of rats' spermatogenic cell, increased Bax expression and decreased Bcl-2/Bax ratio. The mechanism of impaired male reproduction is possibly caused by regulation of the related apoptosis gene in the testis.