Abstract： Objective： To study the medication rules of CHEN Xiaodi， the chief physician of Chinese medicine， in the treatment of patients after surgery for tumor based on data mining. Methods： The first effective prescription from CHEN Xiaodi's clinic was selected，the database was established，and the data mining was carried out on natures and flavors of medicine， meridian tropism， medicine efficacy， and compatibility rules by frequency analysis and cluster analysis. The authors had a face-to-face interview with CHEN Xiaodi，and asked for his own opinions and explanations on the mining results. Results：A total of 236 prescriptions were obtained ， involving 183 kinds of Chinese medicinals ， 18 kinds of effects， and 4 518 times of use. There were 40 Chinese medicinals with a frequency higher than 10%，and 11 Chinese medicinals with a frequency higher than 50% ， including Glycyrrhizae Radix et Rhizoma， Poria， Massa Medicata Fermentata， Rhizoma Atractylodis Macrocephalae， Hedyotis Diffusae Herba， Coicis Semen， Amomi Fructus，Pinelliae Rhizoma，Armeniacae Semen Amarum，Aurantii Fructus，and Pseudostellariae Radix. The medicinal natures are mainly cold， warm， and mild； the medicinal flavors are mainly acrid， bitter，and sweet. The meridian tropism of medicinals is mainly the five viscera，with the spleen (stomach) being the first，followed by the lung. There were 8 types of medicinals with a frequency of use higher than 5% ， which were those for supplementing deficiency， for clearing heat， for dissolving phlegm and relieving panting and cough，for promoting urination and percolating dampness，for releasing the exterior， for resolving dampness， for regulating qi， and for promoting digestion. Eleven clustering groups were obtained by high- frequency medicine clustering， which reflected the differentiation and treatment of viscera and bowels centered on the five viscera， and the compatibility of prescriptions with healthy qi deficiency， heat， toxin， phlegm， dampness， wind， and qi stagnation as the main points of differentiation and treatment. Conclusion： The medication rules of CHEN Xiaodi， the chief physician of Chinese medicine， treating patients after surgery for tumor is centered on the five viscera， reinforcing healthy qi and supplementing deficiency，dispelling pathogen and anti-cancer，using both cold and warm medicinals，and combining internal and external causes.