Objective: To explore the medication rules of State Medical Master YAN Zheng-hua's prescriptions with Achyranthis Bidentatae Radix. Method: The prescriptions including Achyranthis Bidentatae Radix that built by Pro. Yan were collected to build a database based on Traditional Chinese Medicine Inheritance Support System (TCMISS). Then the data were analyzed mainly by Apriori algorithm in the data analysis module of TCMISS to acquire the frequency of single medicine

the frequency of drug combinations

the association rules and core drug combinations in 441 prescriptions including Achyranthis Bidentatae Radix. Result: The prescriptions including Achyranthis Bidentatae Radix were commonly used to treat vertigo

rheumatism syndrome

lumbago and other syndromes. The highest frequency used drugs were Paeoniae Radix Rubra

Taxilli Herba

Paeoniae Radix Alba

Salviae Miltiorrhizae Radix et Rhizoma

Leonuri Herba

and so on. The most frequency drug combinations were 'Achyranthis Bidentatae Radix

Paeoniae Radix Rubra'

'Achyranthis Bidentatae Radix

Taxilli Herba'

and 'Paeoniae Radix Rubra

Taxilli Herba' and so on. when the the minimum-confidence was 0.9

the drug association rules were 'Dipsaci Radix-> Achyranthis Bidentatae Radix'

'Paeoniae Radix Alba

Taxilli Herba-> Achyranthis Bidentatae Radix'

'Paeoniae Radix Alba

Paeoniae Radix Rubra

Taxilli Herba-> Achyranthis Bidentatae Radix'

and 'Taxilli Herba-> Achyranthis Bidentatae Radix'

and so on. Conclusion: The drugs in the prescriptions containing Achyranthis Bidentatae Radix that built by Pro. Yan mostly had the effects of promoting blood circulation to remove meridian obstruction

invigorating the liver and kidney and strengthening muscles and bones

which reflected the clear and precise conception of composing formulas.