Abstract：Objective：To analyze the medication rule of WAN Donggui in the treatment of three negative breast cancer in empty window stage by data mining. Methods： Collect the data of outpatient medical records in China- Japan Friendship Hospital from October 15，2016 to April 16，2020，and establish a database of three negative breast cancer prescriptions. The frequency statistics of traditional Chinese medicine and its attributes in medical record data were carried out by Microsoft Office Excel 2013；SPSS statistical 26.0 software was used for cluster analysis of data，and Apriori algorithm was used for correlation analysis of high- frequency traditional Chinese medicine. Results：360 medical records were included，involving 360 prescriptions. High frequency drugs include Astragalus membranaceus， Trichosanthis pericarpium， Ostreae concha， Ranunculi terati radix，etc. Their properties are warm and flat，their tastes are sweet and bitter，and most of them belong to the liver，spleen，lung，heart and kidney meridians.It is most common to deficiency nourishing drugs(1 853 times)，reducing phlegm and relieving masses drugs(801 times) and heat clearing drugs (568 times). Conclusion：When WAN Donggui treats three negative breast cancer，it is important that differentiation of diseases and differentiation of body，combining the killing with kindness and eliminating evil， mostly with soothing the liver and strengthening the spleen， eliminating phlegm and dispersing heat，clearing away heat and detoxifying.Pay attention to cultivating soil and consolidating foundation，balance yin and Yang，and overcome hardness with softness.