Objective To investigate the change rules of the lumbar vertebral bone marrow fat fraction(FF)and T2* values at different bone mineral density(BMD)groups,and their relevances and the applications on the diagnosis of the primary osteoporosis. Methods The patients who underwent the dual energy X-ray absorptiometry(DXA)and the routine lumbar MRI scan,mDIXON-Quant scan were collected,and the BMD,T-score,FF and T2* values of L1-L4 were measured.According to the T-score,the vertebral bodies were divided into the normal group,the osteopenia group and the osteoporosis group.The differences of the FF,T2* values and BMD between each group were analyzed by one-way analysis of variance,and their correlations with BMD were analyzed by Pearson correlation,the diagnostic effects of them were evaluated by receiver operating characteristic curve(ROC curve).Results The differences of the FF ,T2 * values and BMD among the three groups were statistically significant (P < 0 .05) .The correlations of the FF and T2 * values with BMD were negative (r = - 0 .628 ,P < 0 .05 and r = - 0 .468 ,P < 0 .05 ,respectively) .The area under curve (AUC) of the FF and T2 * values were 0 .82 ± 0 .03 ,0 .79 ± 0 .03 ,respectively .Conclusion mDIXON-Quant which can accuratly quantify fat content could evaluate the lumbar vertebral bone marrow fat content ,reflect the changes of the bone quality ,provide valuable information for the diagnosis of osteoporosis ,and is helpful to predict the risks of the lumbar fragility fracture.