Objective To study the application rules of pungent flavor drugs in the formulas for treating constipation guided by moistening therapy with the drugs of pungent flavor. Methods Formulas of treating constipation in Prescription of Traditional Chinese Medicine Dictionary（《中医方剂大辞典》） were collected. With the R language and R-studio software

the methods of data-mining including association rules and Apriori algorithm were used to extract and analyze the frequency of single medicinal herb

the drug combinations

and the association rules in core drug combinations. Results A total of 405 prescriptions on treating constipation with the drugs of pungent flavor were included

and 44 core drug compositions and 20 association rules were obtained. All of the association rules obtained above were positively correlated

with a confidence greater than 1

while 18 of them were greater positively correlated with a confidence greater than 3. The high frequency drugs of pungent flavor were Danggui（Radix Angelicae Sinensis）

Zhiqiao（Fructus Aurantii）

Muxiang（Radix Aucklandiae）

Binlang（Semen Arecae）

etc. The drugs most commonly combined with the above high frequency drugs were Dahuang（Radix et Rhizoma Rhei）

Huomaren（Fructus Cannabis）

Yuliren（Semen Pruni）

Taoren（Semen Persicae）

etc. Moreover

a total of 70 prescriptions without the drugs of pungent flavor and treating constipation were included. Nine core drug compositions and 5 association rules were obtained

which were all positively correlated

with a confidence greater than 1

while 1 of them were positively correlated with a confidence greater than 3. Prescriptions without pungent flavor drugs usually containe following drugs

Dahhang（Radix et Rhizoma Rei）

Gancao（Radix Glycyrrhizae）

Qianniuzi（Semen Pharbitidis）

Zhizi（Fructus Gardeniae） and Huangqin（Radix Scutellariae）

and they were often compatible with herbs for purgation

clearing heat and norishment. Conclusion Formulas treating constipation often composited with the herbs of pungent flavor and yin-tonifying medicinal

combined with the intestines-moistening and qi-moving medicinal

for their functions of engendering body fluid

moving qi

moistening dryness and relaxing the bowels.