Objective To explore the value of ultrasound and ultrasound-guided lymph node fine needle aspiration (FNA) cytology in preoperative evaluation of triple-negative breast cancer lymph node metastasis. Methods Female patients confirmed to be triple-negative breast cancer in our hospital were recruited as subjects. Multi-faceted examination of the detected lymph nodes was performed to observe the morphology, size, long diameter/short diameter, cortical echo, lymphatic portal structure, lymph node cortical thickness and blood supply. Ultrasound-guided FNA cytology was performed on ultrasound or clinically suspected axillary lymph nodes to evaluate the diagnostic efficacy of ultrasound examination and ultrasound-guided FNA cytology of axillary lymph nodes. Logistic regression was used to establish a mathematical model for multi-index combined diagnosis of axillary lymph node metastasis in triple-negative breast cancer, and the diagnostic value of the model was analyzed by ROC curve. Results Pathological results showed that 35 cases in the metastatic group and 31 cases in the reaction group. L/S ≤ 2, marginal morphology irregularities and missing lymphatic portal had significant effects on lymph node metastasis (all P<0.05). The diagnostic sensitivity and specificity of ultrasonography for metastatic axillary lymph nodes in triple-negative breast cancer were 68.57% and 64.52%, respectively. The sensitivity and specificity of ultrasound-guided FNA for metastatic axillary lymph nodes in triple-negative breast cancer were 85.71% and 83.87%, respectively. The combined fitting equation was logit(P) = -5.301 + 2.860* aspiration result + 3.259 * lymphatic portal + 2.326 * marginal morphology + 2.081 * L / S. Its AUC was 0.959, and the best diagnostic point was 0.510. The sensitivity was 88.57%, and the specificity was 96.77%. Conclusion The accuracy of FNA combined with ultrasound in the diagnosis of metastatic lymph nodes is better than FNA alone.