BACKGROUND. According to the International osteoporosis foundation, the incidence of osteoporose in men is increasing rapidly. Some investigations mention the serum testosterone hormone decreases by aging and may cause of osteoporose. Our study was aimed to evaluate relation between serum total testosterone and bone mineral density in men. MATEREALS AND METHOD. Relatively healthy 624 men aged between 18-87 were randomly selected from Mongolian 4 provinces and Ulaanbaatar city. Specially designed questionnaire was used in the survey. And some of measurement, Weight, height and BMI, was measured. Bone mass density was diagnosed according to the WHO criteria by the T-score. Serum total testosterone level were described by using ELISA kit (Eucardio Laboratory, Inc. USA) at the laboratory of MHI.The statistical result was analyzed by SPSS 22 program. RESULTS. The subjects mean age was 48.56±16.63, with a range of 18-87. The mean SOS was -4055.23±228.89. And the osteoporse was 14.6% (n=91) in all of participants. 152 participants were randomly selected from all participants and classified 2 groups(case and control) according to WHO osteoporosis criteria and evaluated relation between serum total testosterone and bone mineral density. The mean of serum total testosterone level was significantly low (8.80±2.67) in case group than (9.33±2.44) control group (p<0.05). Our study showed that positive correlation between bone mass density values at testosterone hormone (r=0.17 p<0.034). CONCLUSION. Our study showed decreased serum total testosterone hormone affected to decrease of bone mineral density.