To explore composition rules of TCM tranquilizer prescriptions.Methods：The tranquilizer prescriptions in “The New National Medicine” were collected to build a database based on traditional Chinese medicine inheritance assist system. 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 tranquilizer prescriptions, the highest frequently used drugs were Poria Cocos Wolff, Radix Glycyrrhizae, Angelica sinensis, Radix Ophiopogonis, Cinnabaris. The most frequent drug combinations were “Angelica sinensis, Poria Cocos Wolff”, “Poria Cocos Wolff, Parched Semen Ziziphi Spinosae”, “Radix Glycyrrhizae, Poria Cocos Wolff”. The drugs with a high degree confidence coefficient of association rules included “Calculus Bovis, Cinnabaris”, “Semen Ziziphi Spinosae, Poria Cocos Wolff”. The new prescriptions contained Poria Cocos Wolff, Parched Semen Ziziphi Spinosae, Radix Rehmanniae Preparata, Fructus Schisandrae Chinensis, Radix Salviae Miltiorrhizae, Radix Ophiopogonis, and Radix Rehmanniae Exsiccata.Conclusion：Chinese medicine drugs in tranquilizer prescriptions usually have the effects of nourishing the blood, calming mind, benefiting the qi, replenishing the yin and quieting the spirit.