Abstract: Objective: To identify differentially expressed proteins in the lymph fluid of rabbits with breast cancer lymphatic metastasis and normal rabbits, and to analyze and verify using proteomics technology. Materials and Methods: Rabbits with breast cancer lymph node metastasis and healthy rabbits were selected. Lymph fluids were precisely extracted under the guidance of percutaneous contrast-enhanced ultrasound (CEUS). Label-free quantitative proteomics (LFQ) was used to detect and compare differences, and differential protein expression was obtained. Bioinformatics analysis was performed using KEGG and GO analysis software, selecting the most significantly differentially expressed proteins. Finally, parallel reaction monitoring technology (PRM) was applied for validation. Results: A total of 547 significantly differentially expressed proteins were found in this study, including 371 upregulated proteins and 176 downregulated proteins. They were mainly involved in various cellular and metabolic pathways, including upregulated proteins such as BLVRA, IDH2, and downregulated proteins such as PDXK. The upregulated proteins PDIA3, PRKAR1A, and ABCC4 participated in immune regulation, endocrine regulation, and anti-tumor drug resistance regulation, respectively. Conclusion: These proteins are involved in the pathophysiological processes of tumor development and metastasis, and can be used as predictive indicators for breast cancer metastasis and as new targets for treatment.