To reveal the medication rules of external application of Chinese medicines based on syndrome differentiation in the treatment of cancer pain by the data mining method.Methods:The related clinical studies or empirical analysis were retrieved from literature databases.A database of Chinese medicines used in the prescriptions was established in Excel.The use frequency，nature，taste，and tropism of the Chinese medicines were counted，and the cluster analysis in SPSS and the association rule analysis in Clementine were performed to explore the medication rules.Results:A total of 187 studies were included，involving 190 prescriptions and 183 Chinese medicines.Olibanum and Myrrha had the highest use frequency.The medicines with warm or cold nature，bitter taste，tropism to the liver，spleen，and heart meridians，and blood-activating and stasis-resolving activity had higher frequency.The results of association rule analysis showed that Olibanum and Myrrha had the highest confidence.The cluster analysis revealed 7 medicine pairs ad a three-medicine combination.Conclusion:External application of Chinese medicines for cancer pain follows the treatment principles of activating blood，resolving stasis，warming and resolving phlegm and fluid retention，and clearing heart to relieve pain.