To investigate composition rules of Chinese patent drugs with tonifying spleen. Methods:The prescriptions of Chinese patent drugs with tonifying spleen in “The New National Medicine” were collected to build a database. The methods of association rules with apriori algorithm and complex system entropy cluster were used to achieve the frequency of medicines and association rules between drugs. Results:The data-mining results indicated that in the prescriptions of Chinese patent drugs with tonifying spleen, the most frequency used drugs were Poria Cocos Wolff, Rhizoma Atractylodis Macrocephalae, Radix Glycyrrhizae, Radix Codonopsitis, Pericarpium Citri Reticulatae. The most common drug combinations were” Rhizoma Atractylodis Macrocephalae, Poria Cocos Wolff”,” Radix Glycyrrhizae, Poria Cocos Wolff”,” Radix Glycyrrhizae, Rhizoma Atractylodis Macrocephalae”. The drugs with a high degree confidence coefficient of association rules include “Pericarpium Citri Reticulatae->Semen Dolichoris”, “Pericarpium Citri Reticulatae->Pinellia ternata”. Conclusion:There are not only the common drugs tonifying spleen, but also drugs regulating the flow of vital energy, removing obstruction toit, and helping digest.