Objective To ananlyze the relationship between bone mineral density and sex hormone in male patients with obstructive sleep apnea hypopnea syndrome (OSAHS). Methods The study recruited 88 male patients with OSAHS aged 45-60 years in our hospital from October 2014 to October 2016 as an OSAHS group, and 30 healthy subjects without OSAHS as a control group. The general information and PSG parameters were recorded, the bone metabolic markers and bone mineral density of lumbar spine 1-4 (L1-4) and femoral neck (Neck) were measured, and the expressions of serum sex hormone (E2, P, T, FSH, LH and PRL) were determined by chemical luminescence immunity analyzer. The differences in above indexes between two groups and their correlation with bone mineral density were analyzed. Results Smoking rate, drinking rate, neck circumference and body mass index (BMI) of the OSAHS group were significantly higher than those of the control group. Compared with the control group, beta crosslaps (β-CTX, a bone metabolic marker) was significantly higher [(0.53±0.14) ng/ml vs. (0.47±0.15) ng/ml], the bone mineral density of L1-4 and Neck was significantly lower [(0.92±0.12) g/cm2 vs. (1.08±0.08) g/cm2, (0.91±0.11) g/cm2 vs. (1.06±0.13) g/cm2], and the serum testosterone was significantly lower in the OSAHS group [(267.32±89.56) ng/dlvs. (315.68±78.49) ng/dl] (all P<0.05). The result of Pearson correlation analysis showed that apnea hypopnea index (AHI) was negatively correlated with bone mineral density of L1-4 and Neck (bothP<0.001), lowest oxygen saturation (LSaO2) and testosterone were positively correlated with bone mineral density of L1-4 and Neck (all P<0.01). Conclusions The risk of suffering from osteoporosis is higher in male OSAHS patients and it is closely related to the degree of hypoxia. The decrease of testosterone may be one of the mechanisms.