Object: To assess bone mass density in new diagnosed Grave’s disease. Subjects: 60 Grave’s disease patients and 50 normal people that visited at outpatient department for required service, Bach Mai hospital, from October 2017 to July 2018. Methods: Cross-sectional study. Results: 6,66% of patients had osteoporosis at neck of thigh bone and this rate was 3,33% at spine. The bone mass density in new diagnosed Grave’s disease was lower than normal people. At neck of thigh bone: bone mass density in Grave’s disease was - 0,89 ± 1,07 (T - score) but only - 0,58 ± 1,06 (T - score) in control group (p > 0,05). At spine: bone mass density in Grave’s disease was - 0,35 ± 1,22 (T - score) and in control group was 0,068 ± 1,06 (T - score) (p < 0,05). Conclusions: There was no correlation between thyroid volume and bone mass density.