[Objective]To investigate the clinical diagnostic value of the MRI IDEAL-IQ method for the determination of bone marrow fat content (FF,%) in the lumbar spine for osteoporosis, and to analyze the correlation between fat fraction and bone mineral density and bone metabolic indexes. [Methods] Patients who underwent both conventional serial and IDEAL-IQ serial scans of the lumbar spine, dual-energy X-ray bone densitometry and bone metabolic index tests in the Department of Orthopedics of our hospital from January 2022 to February 2023 were collected. The results of vertebral body (L1-L4) fat fraction, bone density and bone metabolic indexes were measured and recorded. According to the T value, the patients could be divided into three groups: normal bone mass group, reduced bone mass group and osteoporosis group. One-way analysis of variance (ANOVA) was performed to compare the differences among the three groups. LSD method was used for pound-for-pair comparison among the three groups. Pearson method was used to analyze the correlation between FF values and BMD, BMI, PⅠNP and β-CTX. And finally, the efficacy of various tests in diagnosing OP was tested by ROC (subject operating characteristic curve). [Results] A total of 91 cases were collected, including 15 cases in the normal bone mass group, 33 cases in the reduced bone mass group and 43 cases in the osteoporosis group. There were significant differences in FF values and β-CTX (p0.05) among the three groups (p<0.05), but no significant differences in P I NP among the three groups (p>0.05). There was a statistically significant difference in FF values between the osteoporosis group and the other two groups (p<0.05), and the P value between the reduced bone mass group and the normal bone mass group was 0.43 (p>0.05), with no statistically significant difference. The difference between β-CTX levels in the normal bone mass group and the other two groups was statistically significant (p < 0.05), and the p-value between the osteoporosis group and the reduced bone mass group was 0.53 (p > 0.05), with not statistically significant. FF values were moderately negatively correlated with BMD (r = -0.396, p < 0.05). FF values were weakly positively correlated with β-CTX (r = 0.238, p>0.05). There was no correlation between FF and PINP (r=0.081, p>0.05). The area under the ROC curve (AUC) of FF values was 0.786. When the diagnostic threshold was 77.99%, the sensitivity and specificity were relatively optimal, which were 86.00% and 67.77% respectively. [Conclusion] The FF values imaged by MRI IDEAL-IQ technique are negatively correlated with BMD and BMI and positively correlated with β-CTX, which can provide valuable information for the clinical diagnosis of osteoporosis.