Abstract: Objective To explore the diagnostic value of magnetic resonance imaging(MRI) in the detection of small lymph node(LN) metastasis and its effect on radiotherapy target volume design in cervical cancer patients. Methods We collected 37 patients with cervical cancer diagnosed pathologically in Sichuan cancer hospital.They were all received preoperative MRI scan and enhanced scan. Combined with T1WI enhanced sequence, the longest diameter and shortest diameter of visible lymph nodes on T2WI were measured respectively，and the morphological features such as enhancement patterns，extra capsular spread(ECS), edge of the lymph nodes andcapsular invasion were recorded. Results Short diameter of metastatic LN was longer than that of non-metastatic LN statistically(P=0.01).Area under curve(AUC) of short diameter in receiver operator characteristic curve(ROC) was larger than those of long diameter and ratio of long-toshort diameter, which showed a more important diagnosis value.When short diameter≥9 mm was choosed as the standard of metastatic LN，the sensitivity,specificity and accuracy were 57.14%,91.67%and 75.56%，respectively.If LN with short diameter≥9,10 mm as GTV-N(gross tumor volume-node) in this experiment were exposed to positive LN dose irradiation,42.86%, 80.95% of malignant LNs may receive insufficient dose radiation. Conclusion MRI has certain value in diagnosing small lymph node metastasis from cervical cancer. It is necessary to conduct prophylactic radiotherapy to pelvic lymph node and a radical cure dose irradiation to small lymph node highly suspected to be malignant.